111. Minimum Depth of Binary Tree
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.
Note: A leaf is a node with no children.
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: 2
Example 2:
Input: root = [2,null,3,null,4,null,5,null,6]
Output: 5
Constraints:
- The number of nodes in the tree is in the range [0, 105].
- -1000 <= Node.val <= 1000
/**
* 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;
}
int left = minDepth(root.left);
int right = minDepth(root.right);
if(left==0||right==0){
return left+right+1;
}
return left<right?left+1:right+1;
}
}