Ex3 -Backtraking

#include <stdio.h>
#include <stdlib.h>

#define natural unsigned short
#define maxN 10000
unsigned v[maxN], n;
static char st[] = { 0, 0, 1, 2};
natural m, p, q;
void Init(natural k) {
    v[k] = 0;
}
natural Succesor(natural k) {
    if (v[k] < 3) {
        v[k]++;
        return 1;
    }
    return 0;
}

natural Valid(natural k) {
    return 1;
}

natural Solution(natural k) {
    return (k == n);
}

void Print() {
    natural i;

    for (i = 1; i <= m; i++)
        printf("0");
    for (i = 1; i <= p; i++)
        printf("1");
    for (i = 1; i <= q; i++)
        printf("2");
    for (i = 1; i <= n; i++)
        printf("%d", st[v[i]]);

    printf("\n");
}

void Back() {
    natural k = 1, isS, isV;
    Init(k);
    while (k > 0) {
        isS = 0; isV = 0;
        if (k <= n)
            do {
                isS = Succesor(k);
                if (isS) isV = Valid(k);
            } while (isS && !isV);
            if (isS)
                if (Solution(k))
                    Print();
                else {
                    k++;
                    Init(k);
                }
            else
                k--;
    }
}

int main() {
    do {
        system("cls");
        printf("n = "); scanf("%d", &n);
        printf("m = "); scanf("%hu", &m);
        printf("p = "); scanf("%hu", &p);
        printf("q = "); scanf("%hu", &q);
    } while (n >= maxN );
    n = n - m - p - q;
    if (n == 0)
        Print();
    Back();
    system("pause");
    return 0;

}