【回溯】八皇后

回溯方法

#include <stdio.h>
#include <stdlib.h>
#define N 8
 int column[N+1];
 int rup[2*N+1];
 int lup[2*N+1];
 int queen[N+1]={0};
 int num;
 void backtrack(int);
 int main()
 {
     int i;
     num=0;
     for(i=1;i<=N;i++)
     column[i]=1;
    
     for(i=1;i<=2*N;i++)
     rup[i]=lup[i]=1;
     backtrack(1);
 system("pause");
 return 0;   
 }
 void backtrack(int i)
 {
   int j,x,y;
   if(i>N)
   {
     printf("\n解答%d\n",++num);
     for(y=1;y<=N;y++)
     {
        for(x=1;x<=N;x++)
        if(queen[y]==x)
           printf("Q");
           else
           printf(".");
        printf("\n");
     }
   }else
   {
      for(j = 1; j <= N; j++) {
            if(column[j] == 1 && rup[i+j] == 1 && lup[i-j+N] == 1) {
                queen[i] = j;
                column[j] = rup[i+j] = lup[i-j+N] = 0; // 
                backtrack(i+1);
                column[j] = rup[i+j] = lup[i-j+N] = 1;
            }
        }
 
   }
    
 }