codeforces 1648B

B. Integral Array

思路：

枚举因子，\([x/y]=z，则y*z<=x<=y*z+y-1\)

代码：

#include <bits/stdc++.h>
#define int long long
int _ = 0, Case = 1;
using namespace std;
#define all(v) begin(v),end(v)
#define nline '\n'

const int N = 1000010;
int cnt[N];
int a[N];
int s[N];
void solve(int Case) {
    int n, c;
    cin >> n >> c;
    for (int i = 1; i <= c; i++) cnt[i] = 0, s[i] = 0;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        cnt[a[i]]++;
    }
    sort(a + 1, a + 1 + n);
    for (int i = 1; i <= c; i++) {
        s[i] = s[i - 1] + cnt[i];
    }
    for (int i = 1; i <= c; i++) {
        if (!cnt[i]) continue;
        int x = i;
        int sum = 0;
        for (int j = x; j <= c; j += x) {
            int t = j / x;
            if (!cnt[t]) continue;
            int l = j, r = min(c, j + x - 1);
            sum += s[r] - s[l - 1];
        }

        if (sum != (s[c] - s[x - 1])) {
            cout << "NO" << nline;
            return;
        }
    }
    cout << "YES" << nline;



}

signed main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    for (cin >> _, Case = 1; Case <= _; Case++)
        solve(Case);

    return 0;
}