Balanced Binary Tree
描述
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.
题解
package algorithms
import (
"github.com/ljun20160606/leetcode/algorithms"
)
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
type TreeNode = algorithms.TreeNode
func isBalanced(root *TreeNode) bool {
if root == nil {
return true
}
diff := heightOfTree(root.Left) - heightOfTree(root.Right)
return diff >= -1 && diff <= 1 && isBalanced(root.Left) && isBalanced(root.Right)
}
func heightOfTree(root *TreeNode) int {
if root == nil {
return 0
}
if root.Left == nil && root.Right == nil {
return 1
}
if root.Left == nil {
return heightOfTree(root.Right) + 1
}
if root.Right == nil {
return heightOfTree(root.Left) + 1
}
left := heightOfTree(root.Left)
right := heightOfTree(root.Right)
if left > right {
return left + 1
}
return right + 1
}