Pejman Moghadam / C-programming

C - The N-Queens Problem

Public domain

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#include <stdio.h>

#define MAX 8
int a[MAX];
double count = 0;

main()
{
    permute(0);
    printf("\nCount = %.0f\n", count);
    return 0;
}

permute(int i)
{
    for(a[i] = 0; a[i] < MAX; a[i]++)
    {
            if(i > 0) {
                    int j;
                    for(j = i-1; j >= 0; j--)
                            if(cross_check(i,j,a[i],a[j]))
                                    break;
                    if(j != -1) continue;
            }
            if(i + 1 < MAX) {
                    permute(i+1);
            } else {
                    count++;
                    show_case();
            }
    }
}

cross_check(int x,int y,int a,int b)
{
    int result = 0;
    if(a==b || abs(a-b)==abs(x-y)) result=1;
    return result;
}

show_case()
{
    int i,j;

    printf("No: %.0f \nResult: ", count);
    for(i=0; i<MAX; i++)
            printf("%d", a[i]);
    printf("\n");

    for(j = 0; j < MAX; j++)
    {
            for(i = 0; i < MAX*2+1; i++)
                    printf("---");
            printf("\n");
            for(i=0; i < MAX*2+1; i++)
                    if(a[j]*2+1 == i) 
                            printf("QQQ");
                    else if(i%2 == 0) 
                            printf(" | ");
                    else 
                            printf("   "); 
            printf("\n");
    }
    for(i = 0; i < MAX*2+1; i++)
            printf("---");
    printf("\n");
    getchar();
}

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BY: Pejman Moghadam
TAG: c, queens
DATE: 2011-12-03 00:37:53

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