【发布时间】：2021-05-27 16:57:41
【问题描述】：
我尝试编写骑士之旅问题（8X8 板），但不知何故我无法让它工作。
我没有探索所有可能的骑士动作，而是将其存储并一一迭代，但是 程序在打印结果之前被终止。
在 cmets 中标记错误代码和（无耻复制）工作代码。
提前致谢:)
*if the board is traversed, print answer and return
* find all possible moves from given position
* for everyPosition in possiblePosition
* place the knight at everyPosition
* call the same function for the new position
* remove the knight from that position
import java.util.*;
import java.util.Map.Entry;
class Solution {
static int [][] res;
static int N;
static int row[];
static int col[];
public static void init(int n) { //initialize the array
res=new int[n][n];//n or N is the size of board which is 8
N=n;
for(int i=0;i<res.length;i++) {
for(int j=0;j<res[0].length;j++) {
res[i][j]=-1;
}
}
}
public static void print(int[][] res) { //helper function to print the 2d array
for(int i=0;i<res.length;i++) {
for(int j=0;j<res[0].length;j++) {
System.out.print(res[i][j]+" ");
}
System.out.println();
}
System.out.println();
}
static boolean isValid(int r,int c){//check if the knight's move is inside the board then return true(<8 && >0)
return (r>=0 && c>=0 && r<N && c<N && res[r][c] == -1);
}
public static boolean solve(int a,int b,int sizeOfBoard,int count,int row[],int col[]) {
if(count==64)//if the board is traversed
{
System.out.println(":)");
print(res);
return true;
}
//**buggy code start**
ArrayList<ArrayList<Integer>>possibleKnightMoves=possibleKnightMoves(a,b,sizeOfBoard);
for(int i=0;i<possibleKnightMoves.size();i++) {//iterate over every possible knight move and check if the knight can be placed there or not
possibleKnightMoves=possibleKnightMoves(a,b,sizeOfBoard);
int x= possibleKnightMoves.get(i).get(0);
int y= possibleKnightMoves.get(i).get(1);
if(isValid(x,y)) {
res[x][y]=count;
if(solve(x,y,sizeOfBoard,count+1,row,col)) {
return true;
}else
{res[x][y]=-1;
}
}
}
//**buggy code end**
//**perfect working code, uncomment me and comment the buggy code(only for reference)**
// for(int i=0;i<N;i++) {
// int x=a+row[i];
// int y=b+col[i];
// if(isValid(x,y)) {
// res[x][y]=count;
// if(solve(x,y,sizeOfBoard,count+1,row,col))
// return true;//knight can be placed
// else
// res[x][y]=-1;
//
// }
//
// }
//**perfect working code end**
return false;//knight cant be placed at the square
}
public static ArrayList<ArrayList<Integer>> possibleKnightMoves(int a,int b,int sizeOfBoard) {
int x=a;
int y=b;
ArrayList<ArrayList<Integer>> result= new ArrayList<ArrayList<Integer>>();
for(int i=0;i<N;i++) {
x=x+row[i];// x,y represent all the possible knight moves from knight's current position
y=y+col[i];
result.add(new ArrayList<Integer>(Arrays.asList(x,y)));//add the moves to all possible moves list
}
return result;
}
public static void knightTour(int n) {
init(n);
res[0][0]=0;//set starting position
int array[]={2, 1, -1, -2, -2, -1, 1, 2 };//array 1 and array 2 represent the set of knight moves from (x,y) eg: x+2,y+1
row=array;
int array2[]={1, 2, 2, 1, -1, -2, -2, -1 };
col=array2;
solve(0,0,n,1,array,array2);//starting from 0,0 with count =1 as knight is already paced on 0,0
}
public static void main(String args[]) {
N=8;
knightTour(8);
init(8);
res[3][3]=1;
}
}
【问题讨论】：
-
你的问题是什么？
-
但是您在
main方法中没有打印任何内容....当然，程序在打印结果之前会被终止。 -
理想情况下应该在计数达到 64 时立即打印结果 - if(count==64)//如果板被遍历 { System.out.println(":)" );打印（分辨率）；返回真； }
-
@SomeDude 当我运行上面的代码时，它在打印结果之前就被终止了，所以我的问题是我到底做错了什么
-
在
possibleKnightMoves方法中，x=x+row[i];不应该是x=a+row[i];吗？与 Y 相同
标签： algorithm data-structures backtracking knights-tour