BFS场景样例测试--最短路径--用Java实现

标签：TreeNode cur -- 样例 int step new Java left

我们今天研究下最短路径 用BFS来实现

 

首先确定数据结构

/**
 * 二叉树数据结构节点
 */
public class TreeNode {

    int value;
    TreeNode left;
    TreeNode right;

    public TreeNode(int val){
        this.value = val;
    }
}

然后走下场景的代码

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.List;
import java.util.Queue;

public class BFSDemoTwo {
    /***
     * 找出起点到终点最短距离 
     * @param start
     * @return
     */
    public int distanceOrder(TreeNode start,TreeNode target){

        Queue<TreeNode> q = new ArrayDeque<>();

        // 将开始节点加入队列
        if(null != start){
            q.offer(start);
        }


        int step = 0;

        while (!q.isEmpty()){
            int sz = q.size();

            // TODO  这里有优化空间 暂时不修改
            List<Integer> num = new ArrayList<>();

            for (int i = 0; i < sz; i++) {
                TreeNode cur = q.poll();

                if(cur.value == target.value){
                    return step;
                }

                // 将左右节点加入队列 以备下一轮迭代
                if(cur.left!=null){
                    q.offer(cur.left);
                }

                if(cur.right!=null){
                    q.offer(cur.right);
                }

                num.add(cur.value);

            }
            step++;

        }
        return step;
    }

    public static void main(String[] args){

        // 构建测试数据

        TreeNode root = new TreeNode(9);
        TreeNode node1 = new TreeNode(1);
        TreeNode node2 = new TreeNode(2);
        TreeNode node7 = new TreeNode(7);
        TreeNode node5 = new TreeNode(5);
        TreeNode node4 = new TreeNode(4);

        root.left = node1;
        root.right = node2;
        node2.left = node7;
        node2.right = node5;
        node7.left = node4;

        BFSDemoTwo bfsDemoTwo = new BFSDemoTwo();

        int step = bfsDemoTwo.distanceOrder(root,node4);
        System.out.println("步数是："+step);

    }
}

 

运行结果

 

 

标签：TreeNode,cur,--,样例,int,step,new,Java,left
From： https://www.cnblogs.com/zhou-789profession/p/17004644.html