recursive_permutation.c

#include<stdio.h>

int n, cnt = 0;
int b[100];
int vst[100];
FILE *fi, *fo;

void rc(int i)
{
    if (i > n){
        ++cnt;
        for (long j = 1; j <= n; ++j)
            fprintf(fo, "%i", b[j]);
        fprintf(fo, "%s", "\n");
        return;
    }
    for (long j = 1; j <= n; ++j)
        if (!vst[j]){
            vst[j] = 1;
            b[i]=j;
            rc(i+1);
            vst[j] = 0;
        }
}

int main()
{
    fi = fopen("in", "r");
    fscanf(fi,"%d", &n);
    fclose(fi);

    fo = fopen("out", "w");
    rc(1);
    fprintf(fo, "qtt: %i", cnt);
    fclose(fo);

    return 0;
}