196 permutations

ViewController.swift

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.main.sync(execute: task)
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .background).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.main.async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
This is when I realized I should try multiple times 
output: 
1
2
3
5
4

OR 

1
5
2
4
3

OR 

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3

OR 

1
5
2
4
3

OR 

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3
 OR

1
5
2
4
3

OR 

1
5
2
4
3

The swift compiler has a typing delay after running this.
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3

OR

1
2
5
4
3

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3

OR

1
5
2
4
3

OR

1
2
5
4
3
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.main.sync(execute: task)
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
2
5
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
4
5

OR 

1
2
3
5
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR 

1
5
2
3
4

OR 

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR 

1
5
2
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR 

1
2
5
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .background).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR 

1
2
3
4
5

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR 

1
5
2
3
4

OR

1
2
5
3
4
*/

func test() {
    print(1)
    DispatchQueue(label: "com.test.mySerialQueue").async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3

x3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3

OR

1
5
2
4
3

x2
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
5
4

OR

1
5
2
3
4

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3

OR

1
5
2
4
3

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
5
4

OR

1
2
3
4
5

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3
x3

OR

1
5
2
4
3
x5
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
4
5

OR

1
2
5
4
3

OR

1
2
4
3
5

*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.main.sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR
1
5
2
3
4

OR

1
2
5
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
2
5
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
4
5

OR

1
5
2
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .background).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
2
3
4
5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4
x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInitiated).async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x2

OR

1
2
3
4
5

OR 

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x2
OR
1
5
2
4
3
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x4

OR 

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x2

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3

OR

1
5
2
4
3

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3

OR

1
5
2
3
4

x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3

OR

1
5
2
4
3

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.main.sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .background).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .utility).async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x3
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3
x3

OR
1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3

OR

1
5
2
4
3

x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3
x2

OR

1
2
5
4
3

OR

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x3
OR
1
2
5
4
3

*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
4
5

OR

1
2
4
3
5

OR

1
2
5
4
3

*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3
x3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
5
3

OR
1
2
5
4
3

OR

1
5
2
4
3

*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.main.sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4
x2

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4
x2

OR

1
2
3
4
5

*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4

OR

1
5
2
3
4
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
5
2
3
4
x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
2
3
4
5

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .background).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
3
4
5
x3

OR

1
2
5
3
4
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4
x2

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .userInteractive).async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
3
4

OR

1
2
3
4
5
x2
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x3
OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue(label: "com.test.mySerialQueue").async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x6
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x3
OR

1
5
2
4
3
x3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x2

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x3

OR

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x5 
Notice numbers printing sequentially, not all instantaneous. 
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
4
3
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.main.sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x5
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .utility).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x5
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x5
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .background).async {
        print(2)
        synced(self) {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
5
2
3
4
x6
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.main.async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
5
4
3
x2

OR

1
5
2
4
3
x2
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.global(qos: .userInitiated).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*
output: 
1
2
4
3
5
x2

OR

1
5
2
4
3
x3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.global(qos: .utility).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
2
4
5
3
x2

OR

1
5
2
4
3
x2
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.global(qos: .userInteractive).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
2
4
3
5

1
5
2
3
4

1
5
2
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.global(qos: .background).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
5
2
4
3

1
5
2
4
3

1
5
2
4
3
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.global(qos: .unspecified).async {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
5
2
3
4

1
5
2
3
4


1
5
2
4
3

1
5
2
4
3
*/


func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        DispatchQueue.main.sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
5
2
3
4


1
5
2
3
4


1
2
5
3
4
*/

func test() {
    print(1)
    DispatchQueue.global(qos: .unspecified).async {
        print(2)
        ispatchQueue(label: "com.test.mySerialQueue").sync {
            print(3)
        }
        print(4)
    }
    print(5)
}
/*

output: 

1
5
2
3
4

1
5
2
3
4

1
5
2
3
4
*/