Submission #993657

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Source Code Expand

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <vector>

using namespace std;
using ll = long long;

#define all(c) (c).begin(), (c).end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define pb(e) push_back(e)
#define mp(a, b) make_pair(a, b)
#define fr first
#define sc second

const ll INF = 1e9;
const ll MOD = 1e9 + 7;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int N, M;
int X[100005];
int cnt[100005];
int mod[100005];
int pena[100005];

int main() {
    cin >> N >> M;
    rep(i, N) cin >> X[i];
    rep(i, N) cnt[X[i]]++;
    rep(i, N) mod[X[i] % M]++;
    int ans = 0;
    rep(i, M / 2 + 1) {
        int a = min(mod[i], mod[M - i]);
        ans += a;
        pena[i] = pena[M - i] = a;
    }
    rep(i, 100) {
        int a = cnt[i] - pena[i%M];
        if (a > 0) ans += a / 2;
    }
    cout << ans << endl;

    return 0;
}

Submission Info

Judge Result