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.
題目
給定一個(gè)二叉樹堆缘，找出其最大深度薛夜。
二叉樹的深度為根節(jié)點(diǎn)到最遠(yuǎn)葉子節(jié)點(diǎn)的距離砸逊。
分析
最簡單的求深度的代碼
代碼
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: The root of binary tree.
* @return: An integer.
*/
public int maxDepth(TreeNode root) {
// write your code here
if (root == null)
{
return 0;
}
int left = maxDepth(root.left);
int right = maxDepth(root.right);
return (left > right) ? left + 1 : right + 1;
}
}
非遞歸的方法
使用有一個(gè)棧即可
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int maxDepth(TreeNode root) {
if (root == null)
return 0;
Deque<TreeNode> stack = new LinkedList<TreeNode>();
stack.push(root);
int count = 0;
while (!stack.isEmpty()) {
int size = stack.size();
while (size-- > 0) {
TreeNode cur = stack.pop();
if (cur.left != null)
stack.addLast(cur.left);
if (cur.right != null)
stack.addLast(cur.right);
}
count++;
}
return count;
}
}
