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);    }}