【Leetcode-easy-111】Minimum Depth of Binary Tree

【Leetcode-easy-111】Minimum Depth of Binary Tree

题目

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

思路

层次遍历二叉树

程序

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int minDepth(TreeNode root) {
if (root == null) return 0;
// if (root.left == null || root.right == null) return 1;

LinkedList<TreeNode> queue = new LinkedList<>();
queue.offer(root);
int level = 0;
while (!queue.isEmpty()){
level ++;
int len = queue.size();
for (int i = 0; i < len; i ++){
TreeNode currNode = queue.poll();
if (currNode.left == null && currNode.right == null)
return level;
if (currNode.left != null) queue.offer(currNode.left);
if (currNode.right != null) queue.offer(currNode.right);
}
}
return level;
}
}