Buying books

#include <stdio.h>
#include <math.h>

#define N 7

float x[] = {
    11.5,
    12,
    12,
    12.5,
    13,
    13,
    14.5
};

char vis[N] = {0};
float temp[N];
int steps[N];
float sol[N];
int solsteps[N];

float sum = 0;
float min = 0;
int f = 0;
int mal = 0;

float roundar(float param) {
    float fractpart;
    double intpart;
    fractpart = modf (param , &intpart);
    if      (fractpart >= 0.75) fractpart = 0.75;
    else if (fractpart >= 0.5 ) fractpart = 0.5 ;
    else if (fractpart >= 0.25) fractpart = 0.25;
    else    fractpart = 0;
    return param; // optionality...
}

void rec(int level, float cobon, float stack) {
    int i;

    if (level == N) {

        if ((!f) || (sum < min)) {
            f = 1;
            min = sum;
            for (i = 0; i < N; i++) sol[i] = temp[i], solsteps[i] = steps[i];
        }
        return;
    }

    for (i = 0; i < N; i++) {
        if (!vis[i]) {
            vis[i] = 1;
            float cost ;
            temp[level] = x[i];
            // there are two possiblities...
            // 1- terminate the stack:
            cost = roundar((1-cobon) * (stack + x[i]));
            sum += cost;
            steps[level] = mal++;
            rec(level+1, (roundar(0.5*cost))/100, 0);
            mal--;
            sum -= cost;

            // 2- don't terminate it:
            if (level != N - 1) {
                rec(level+1, cobon, stack + x[i]);
            }

            vis[i] = 0;
        }
    }
}


int main() {
    int i = 0;
    rec(0, 0, 0);
    printf("min=%f\n", min);
    for (i = 0; i < N; i++)
        printf("%.2f (%d)%s", sol[i], solsteps[i], i==N-1 ? "\n":" => ");
    return 0;
}