Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the short

Posted 2021-12-29 q-1993

/**
 * Definition for binary tree
 * public class TreeNode 
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x)  val = x; 
 * 
 */
import java.util.*;
public class Solution 
    public int run(TreeNode root) 
        if(root == null)
            return 0;
        
        Queue<TreeNode> s  = new LinkedList<TreeNode>();
        s.add(root);
        int start = 0;
        int end = 1;
        int level = 1;
        while(s!=null)
            TreeNode node = s.poll();
            start++;
            if(node.left == null && node.right == null)
                return level;
            
            if(node.left!=null)
                s.add(node.left);
            
            if(node.right!=null)
                s.add(node.right);
            
            if(start == end)
                start = 0;
                level++;
                end = s.size();
            
        
        return level;