//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

public class Solution {
    public int run(TreeNode root) {
        if(root == null) return 0;
        if(root.left == null && root.right != null){
           return run(root.right) + 1;
        }
        if(root.left != null && root.right == null){
            return run(root.left) + 1;
        }
        return Math.min(run(root.left),run(root.right))+1;
    }
}