Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
思路:
树的递归遍历演化,从最简单的深度为1的树想,一个节点 maxdep=1。
父节点是左右两个孩子中最大的深度+1
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int maxDepth(TreeNode root) {
int leftdepth,rightdepth;
if(root==null){
return 0;
}
if(root.left==null && root.right==null){
return 1;
}
leftdepth=maxDepth(root.left)+1;
rightdepth=maxDepth(root.right)+1;
if(leftdepth>rightdepth)
return leftdepth;
else return rightdepth;
}
}
简化方法(来源互联网)
if(root == NULL) return 0;
return max(maxDepth(root.left), maxDepth(root.right))+1;