Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

 

Depth(root)=min(Depth(right),Depth(left))+1

/**
 * 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 min=Integer.MAX_VALUE/2;
    public int minDepth(TreeNode root) {
        if(root == null){
            return 0;
        }
        preOrder(root,1);
        return min;
    }
    
    public void preOrder(TreeNode p,int level){
        if(p!=null){
            if(p.left==null&&p.right==null){
                if(level<min){
                    min=level;
                }
            }
            preOrder(p.left,level+1);
            preOrder(p.right,level+1);
        }
    }
}