JZ39 平衡二叉树

func maxDepth(root *TreeNode) int {
    if root == nil {
        return 0
    }  
    //不平衡的时候用-1表示
    left := maxDepth(root.Left)
    right := maxDepth(root.Right)
    
    if left == -1 || right == -1 || abs(left - right) > 1 {
        return -1
    }
    
    return max(left, right) + 1
}

func max(a, b int) int {
    if a < b {
        return b
    }
    return a
}

func abs(c int) int {
    if c < 0 {
        return -c
    }
    return c
}

func IsBalanced_Solution(root *TreeNode) bool {
    if root == nil {
        return true
    }
    
    return maxDepth(root) != -1
}