Educational Codeforces Round 9 D - Longest Subsequence

D - Longest Subsequence

思路：枚举lcm， 每个lcm的答案只能由他的因子获得，类似素数筛搞一下。

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define pii pair<int,int>
#define piii pair<int, pair<int,int> >

using namespace std;

const int N = 1e6 + 10;
const int M = 10 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-6;

int n, m, tot, a[N], cnt[N], id[N];

vector<int> v[N];

void init() {
    for(int i = 1; i <= m; i++) {
        for(int j = i; j <= m; j+= i) {
            v[j].push_back(i);
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; i++) {
        int x; scanf("%d", &x);
        if(x <= m) {
            id[tot] = i;
            a[tot++] = x;
        }
    }

    if(tot == 0) {
        printf("1 0\n");
    } else {
        init();
        for(int i = 0; i < tot; i++) {
            cnt[a[i]]++;
        }

        int mx = 0, ans = 0;
        for(int i = m; i >= 1; i--) {
            int ret = 0;
            for(int t : v[i]) {
                ret += cnt[t];
            }
            if(ret >= mx) {
                mx = ret;
                ans = i;
            }
        }

        printf("%d %d\n", ans, mx);
        for(int i = 0; i < tot; i++) {
            if(ans % a[i] == 0) {
                printf("%d ", id[i]);
            }
        }
        puts("");
    }
    return 0;
}
/*
*/