Leetcode no. 111

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.

/**
* 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 minDepth(TreeNode root) {
if (root== null) return 0;
return helper(root, 0);
}
private int helper(TreeNode root, int depth){
if (root.left== null && root.right== null) return depth+1;
int left=Integer.MAX_VALUE, right=Integer.MAX_VALUE;
if (root.left!= null) left= helper(root.left, depth+1);
if (root.right!= null) right= helper(root.right, depth+1);
return Math.min(left, right);
}
}