華為機試8.25第二題

題目大意： 

給你一個矩陣代表一個闖關方格，英雄最開始在(0,0)處，移動一次耗費1s，闖關方格上的數字代表着倒計時，每過一秒減一，當減到0時該格子無法通過，求到右下角的最短時間

 

BFS搜索加剪枝即可

 

作者：相依相隨
鏈接：https://www.nowcoder.com/discuss/719729?type=post&order=time&pos=&page=3&ncTraceId=&channel=-1&source_id=search_post_nctrack
來源：牛客網

package nowcoder;
 
import java.io.BufferedInputStream;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
 
public class Main48 {
    public static void main(String[] args) {
        new Solve48().solve();
    }
}
 
class Solve48{
    int row,col;
    int[] dx={-1,1,0,0};
    int[] dy={0,0,1,-1};
    private class Node{
        int x;
        int y;
        int hop;
 
        public Node(int x, int y, int hop) {
            this.x = x;
            this.y = y;
            this.hop = hop;
        }
    }
    public void solve(){
        Scanner s=new Scanner(new BufferedInputStream(System.in));
        row=s.nextInt();
        col=s.nextInt();
        int[][] grid=new int[row][col];
        for (int i = 0; i <row ; i++) {
            for (int j = 0; j < col; j++) {
                grid[i][j]=s.nextInt();
            }
        }
        System.out.println(getAns(grid));
 
    }
    private int getAns(int[][] grid){
        if (grid[0][0]<=0){
            return -1;
        }
        int[][] minTime=new int[row][col];
        for (int i = 0; i < row; i++) {
            Arrays.fill(minTime[i],Integer.MAX_VALUE);
        }
        Queue<Node> queue=new LinkedList<>();
        queue.add(new Node(0,0,0));
        while (!queue.isEmpty()){
            Node node=queue.poll();
            int x=node.x;
            int y=node.y;
            int hop=node.hop;
//            System.out.println(x+" "+y+" "+hop);
            if (minTime[x][y]<=hop||grid[x][y]<hop)continue;
            minTime[x][y]=hop;
            if (x==row-1&&y==col-1)return hop;
            for (int i = 0; i < dx.length; i++) {
                int nextX=dx[i]+x;
                int nextY=dy[i]+y;
                if (!inGrid(nextX,nextY))continue;
                queue.add(new Node(nextX,nextY,hop+1));
            }
        }
        return -1;
    }
    private boolean inGrid(int x,int y){
        return x>=0&&x<row&&y>=0&&y<col;
    }
}