hdu 5339 Untitled（回溯）

hdu 5339 Untitled

题目大意：给出n个数字的序列，和一个数a，在n中有m个数$b1,...,bm$使得$__a %b1%b2%...%bm = 0$，求最小的m。

解题思路：回溯。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstdlib>
using namespace std;

const int N = 50;
const int INF = 50;
typedef long long ll;

int n, a, cnt;
int num[N];
int vis[N], ans;
void DFS(int x, int dis) {
    if (dis >= ans) return;
    if (x == 0) {
        if (ans > dis) ans = dis;   
        return;
    }
    for (int i = 0; i < cnt; i++) {
        if (num[i] > x) break;
        if (!vis[i]) {
            vis[i] = 1;
            DFS(x % num[i], dis + 1);
            vis[i] = 0;
        }
    }
}
int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        ans = INF;
        scanf("%d %d", &n, &a); 
        int temp, flag = 0;
        cnt = 0;
        for (int i = 0; i < n; i++) {
            scanf("%d", &temp); 
            if (temp == a || temp == 1) {
                flag = 1;
                break;
            } else if (temp < a) {
                num[cnt++] = temp;
            }
        }
        if (flag) {
            printf("1\n");
            continue;
        }
        sort(num, num + cnt);
        DFS(a, 0);
        if (ans == INF) printf("-1\n");
        else printf("%d\n", ans);
    }
    return 0;
}