Submission #7505854

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Source Code Expand

#include<algorithm>
#include<cassert>
#include<climits>
#include<cmath>
#include<cstring>
#include<deque>
#include<functional>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

using lint = long long;
using P = pair<int, int>;
using LLP = pair<long long, long long>;

#define REP(i, x, n) for(int i = (x), i##_len = int(n) ; i < i##_len ; ++i)
#define rep(i, n) for(int i = 0, i##_len = int(n) ; i < i##_len ; ++i)
#define reps(i, n) for(int i = 1, i##_len = int(n) ; i <= i##_len ; ++i)
#define rrep(i, n) for(int i = int(n) - 1 ; i >= 0 ; --i)
#define rreps(i, n) for(int i = int(n) ; i > 0 ; --i)
#define SORT(x) sort((x).begin(), (x).end())
#define SORT_INV(x) sort((x).rbegin(), (x).rend())
#define TWINS(x) cout << ((x) ? "Yay!" : ":(") << endl

constexpr int IINF = (1 << 30) - 1;
constexpr long long LLINF = 1LL << 61;
constexpr double EPS = 1e-8;

const int dx4[] = {1, 0, -1, 0}, dy4[] = {0, 1, 0, -1};
const int dx8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dy8[] = {0, -1, -1, -1, 0, 1, 1, 1};

template<typename T>
bool chmax(T& a, T b, bool equal = false){
    if(a < b || equal && a == b){
        a = b;
        return true;
    }
    return false;
}

template<typename T>
bool chmin(T& a, T b, bool equal = false){
    if(b < a || equal && a == b){
        a = b;
        return true;
    }
    return false;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, m;
    cin >> n >> m;

    vector<int> x(n);
    map<int, int> cnt;
    rep(i, m + 1){
        cnt[i] = 0;
    }
    rep(i, n){
        cin >> x[i];
        ++cnt[x[i] % m];
    }

    map<int, int> mp;
    rep(i, n - 1){
        int p = x[i] % m;
        if(p == 0){
            continue;
        }else if(x[i] == x[i + 1]){
            ++mp[p];
            ++i;
        }
    }

    int ans = 0;
    for(auto x : cnt){
        if(x.first > m / 2){
            break;
        }
        if(x.first == 0 || (m % 2 == 0 && x.first == m / 2)){
            ans += x.second / 2;
        }else{
            auto it = cnt.lower_bound(m - x.first);
            ans += min(x.second, (*it).second);
            int tmp;
            if(x.second < (*it).second){
                tmp = (*it).second - x.second;
                ans += min(tmp / 2, mp[(*it).first]);
            }else if(x.second > (*it).second){
                tmp = x.second - (*it).second;
                ans += min(tmp / 2, mp[x.first]);
            }
        }
    }

    cout << ans << endl;

    return 0;
}

Submission Info

Judge Result