110. Balanced Binary Tree

Description

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7
Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4
Return false.

Answer

func help(root *TreeNode, res *bool) int {
    if *res == false {
        return 0
    }
    if root == nil {
        return 0
    }
    left := help(root.Left, res)
    right := help(root.Right, res)
    if math.Abs(float64(left)-float64(right))>1 {
        *res = false;
        return 0;
    }
    if left > right {
        return left + 1
    }
    return right + 1

}
func isBalanced(root *TreeNode) bool {
    res := true
    help(root, &res)
    return res
}