Created
November 3, 2017 13:32
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Sum of two binaries, represented through strings.
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| import Foundation | |
| func sum(_ lhs: String,_ rhs: String, carry: Int = 0) -> String { | |
| guard let lhsLast = lhs.last else { | |
| if rhs.count > 0 { | |
| return rhs | |
| } else { | |
| return carry == 1 ? "1" : "" | |
| } | |
| } | |
| guard let rhsLast = rhs.last else { | |
| if lhs.count > 0 { | |
| return lhs | |
| } else { | |
| return carry == 1 ? "1" : "" | |
| } | |
| } | |
| switch (lhsLast,rhsLast,carry) { | |
| case ("0","0",0): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 0) + "0" | |
| case ("0","0",1): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 0) + "1" | |
| case ("1","0",1),("0","1",1): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 1) + "0" | |
| case ("1","0",0),("0","1",0): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 0) + "1" | |
| case ("1","1",0): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 1) + "0" | |
| case ("1","1",1): return sum(String(lhs.dropLast()), String(rhs.dropLast()), carry: 1) + "1" | |
| default: return "" | |
| } | |
| } | |
| let a = "1100" | |
| let b = "1000" | |
| let sumResult = sum(a,b) |
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