【HDOJ】1016 Prime Ring Problem

经典DP，写的可能麻烦了一些。

#include <stdio.h>
#define false 0
#define true  1

int is_prime[];
int is_visit[];
int sequence[];

void DFS(int, int, int);

int main() {

    int i, j, k;
    int n;

    is_prime[] = false;
    is_prime[] = true;

    for (i=; i<=; i++) {
        k = ;
        for (j=; j*j<=i; j++) {
            if (i%j == ) {
                k = ;
                break;
            }
        }
        if (k) {
            is_prime[i] = false;
        } else {
            is_prime[i] = true;
        }

    }

    k = ;

    while (scanf("%d", &n) != EOF) {
        printf("Case %d:\n", ++k);

        DFS(, , n);

        printf("\n");
    }

    return ;
}

void DFS(int num, int order, int end) {
    int i;

    is_visit[num] = true;
    sequence[order] = num;

    if (order == end) {
        if (is_prime[num+]) {
            sequence[order] = num;
            for (i=; i<=end; i++) {
                if (i != end)
                    printf("%d ", sequence[i]);
                else
                    printf("%d\n", sequence[i]);
            }
        }
    } else {
        for (i=; i<=end; i++) {
            if (is_visit[i] == false && is_prime[i+num]) {
                DFS(i, order+, end);
                is_visit[i] = false;
            }
        }
    }
}