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.

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/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
private int min (int a ,int b){
if(a>b)return b;
return a;
}
public int minDepth(TreeNode root) {
if(root==null)return 0;
// if(root.val!=0)return root.val;
if(root.left==null&&root.right==null)return 1;
if(root.left==null){
root.val=minDepth(root.right)+1;
return root.val;
}
if(root.right==null){
root.val=minDepth(root.left)+1;
return root.val;
}
root.val=min(minDepth(root.left),minDepth(root.right))+1;
return root.val;
}
}