Submission #992247

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Source Code Expand

#include <iostream>
#include <fstream>
#include <set>
#include <map>
#include <string>
#include <vector>
#include <bitset>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <cassert>
#include <queue>

#define mp make_pair
#define pb push_back


typedef long long ll;
typedef long double ld;

using namespace std;

int n, m;
int c[120000];
vector<int> c0[120000];
vector<int> c1[120000];

int main() {
	cin >> n >> m;
	for (int i = 0; i < n; ++i) {
		int x;
		cin >> x;
		int y = x % m;
		if (y > m - y)
			c1[m - y].push_back(x);
		else
			c0[y].push_back(x);
	}
	int ans = 0;
	for (int i = 0; i < m; ++i) {
		if ((i + i) % m == 0) {
			ans += (c0[i].size() + c1[i].size()) / 2;
			continue;
		}
		sort(c0[i].begin(), c0[i].end());
		sort(c1[i].begin(), c1[i].end());
		int cc = 0;
		if (c0[i].size() > c1[i].size()) {
			for (int j = 0; j < (int)c0[i].size(); ++j) {
				if (j != (int)c0[i].size() && c0[i][j] == c0[i][j + 1])
					++cc, ++j;
			}
		}
		else {
			for (int j = 0; j < (int)c1[i].size(); ++j) {
				if (j != (int)c1[i].size() && c1[i][j] == c1[i][j + 1])
					++cc, ++j;
			}
		}
		int mx = max(c0[i].size(), c1[i].size());
		int mn = min(c0[i].size(), c1[i].size());
		cc = min(cc, (mx - mn) / 2);
		ans += cc + mn;
	}
	cout << ans << "\n";
	return 0;
}

Submission Info

Judge Result