为什么它总是打印“没有路径” [英] Why it always print "no path"
问题描述
package shortestpath;
import java.util.LinkedList;
import java.util.Scanner;
public class ShortestPath {
public int[] dx = {0,-1};
public int[] dy = {1, 0};
public static int[][] maze = new int[10][10];
public int n;
public int m;
public int[][] dist = new int[10][10];
public boolean valid(int i, int j)
{
return i >= 0 && i < n && j >= 0 && j < m && maze[i][j] == 1;
}
public int bfs(Pair<Integer,Integer> source,Pair<Integer,Integer> destination)
{
for (int i = 0 ; i < 10 ; i++)
{
for (int j = 0 ; j < 10 ; j++)
{
dist[i][j] = (int) 1e9;
}
}
LinkedList<pair> q = new LinkedList<pair>();
q.add(source);
dist[source.first][source.second] = 0;
while (!q.isEmpty())
{
Pair<Integer,Integer> cur = q.get(q.size()-1);
q.pop();
if (cur.first == destination.first && cur.second == destination.second)
{
return dist[cur.first][cur.second];
}
for (int i = 0 ; i < 2 ; i++)
{
int newi = dx[i] + cur.first;
int newj = dy[i] + cur.second;
if (valid(newi,newj))
{
if (dist[newi][newj] > dist[cur.first][cur.second] + 1)
{
dist[newi][newj] = dist[cur.first][cur.second] + 1;
Pair<Integer,Integer> x = new Pair<>(newi,newj);
q.push(x);
}
}
}
}
return -1;
}
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.println("Enter the size of the maze");
int n=sc.nextInt();
System.out.println("Enter the maze");
int m=sc.nextInt();
for (int i = 0 ; i < n ; i++)
{
for (int j = 0 ; j < m ; j++)
{
maze[i][j] = sc.nextInt();
}
}
Pair<Integer,Integer> source = new Pair<Integer,Integer>();
Pair<Integer,Integer> dest = new Pair<Integer,Integer>();
System.out.println("Enter the source");
source.first = sc.nextInt();
source.second = sc.nextInt();
System.out.println("Enter the destination");
dest.first = sc.nextInt();
dest.second = sc.nextInt();
int x = new ShortestPath().bfs(source, dest);
if (x == -1)
{
System.out.print("No Path\n ");
}
else
{
System.out.print("you can go from source to destination by move ");
System.out.print(x);
System.out.print(" moves\n");
}
}
}
我尝试了什么：
i尝试了所有的东西，但我不能定义错误在哪里。
i认为它在这里
What I have tried:
i tried every thing but i cant define where is the error.
i think it in here
public int bfs(Pair<Integer,Integer> source,Pair<Integer,Integer> destination)
{
for (int i = 0 ; i < 10 ; i++)
{
for (int j = 0 ; j < 10 ; j++)
{
dist[i][j] = (int) 1e9;
}
}
LinkedList<pair> q = new LinkedList<pair>();
q.add(source);
dist[source.first][source.second] = 0;
while (!q.isEmpty())
{
Pair<Integer,Integer> cur = q.get(q.size()-1);
q.pop();
if (cur.first == destination.first && cur.second == destination.second)
{
return dist[cur.first][cur.second];
}
for (int i = 0 ; i < 2 ; i++)
{
int newi = dx[i] + cur.first;
int newj = dy[i] + cur.second;
if (valid(newi,newj))
{
if (dist[newi][newj] > dist[cur.first][cur.second] + 1)
{
dist[newi][newj] = dist[cur.first][cur.second] + 1;
Pair<Integer,Integer> x = new Pair<>(newi,newj);
q.push(x);
}
}
}
}
return -1;
}
推荐答案
为什么总是打印无路径
因为代码中存在错误。
最好是获取一个简单的数据集并观察代码在调试器上执行，当你的代码开始做意想不到的事情时，你就接近一个bug。
-----
有一个工具可以让你看到什么你的代码正在做，它的名字是调试器。它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪种期望与现实相符。
当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。
使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量。
调试器 - 维基百科，免费的百科全书 [ ^ ]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html [ ^ ]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html [ ^ ]
调试器在这里向您展示你的代码正在做，你的任务是与它应该做的事情进行比较。
调试器中没有魔法，它没有找到错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。
Because there is a bug on your code.
The best is to get a simple dataset and watch your code perform on debugger, when your code start doing unexpected things, you are close to a bug.
-----
There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[^]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.
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