UnivalCountSolution1.swift

class UnivalCountSolution {
    private var count = 0
    private var testCount = 0
    func soultion(_ root: TreeNode?) -> Int {
        guard let root = root else {
            return 0
        }
        isUnivalSubtree(root)
        return count
    }
    
    private func isUnivalSubtree(_ node: TreeNode) -> Bool {
        testCount += 1
        print("total visit node", testCount)
        if node.left == nil, node.right == nil {
            count += 1
            return true
        }
        
        var isUnival = true
        
        if let left = node.left {
            print("l", left.val)
            isUnival = isUnival && node.val == left.val && isUnivalSubtree(left)
        }
        
        if let right = node.right {
            // 這邊 isUnivalSubtree(right) 沒作用
            print("r", right.val)
            isUnival = isUnival && node.val == right.val && isUnivalSubtree(right)
        }
        
        if isUnival {
            count += 1
        }
        return isUnival
    }
}

let node = TreeNode(5)
node.left = TreeNode(1)
node.left?.left = TreeNode(5)
node.left?.right = TreeNode(5)
node.right = TreeNode(5)
node.right?.right = TreeNode(5)

UnivalCountSolution().soultion(node)

  
/* log
  total visit node 1
  l 1
  r 5
*/