Submission #993123

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Source Code Expand

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <sstream>
#include <vector>
#include <map>
#include <set>
#include <deque>
#include <list>
#include <stack>
#include <queue>
#include <complex>
#include <ctime>
#include<cstdlib>
#define _USE_MATH_DEFINES
#include <math.h>
#include<cmath>
#include <cstdarg> 
#include <iomanip>

#include<unordered_map>
#include<unordered_set>
//#include <arra.y>

//#define  NDEBUG
#include <assert.h>

using namespace std;

#define dprint(Exp,...) if(Exp){fprintf(stderr, __VA_ARGS__);}
#define printe(...) fprintf(stderr, __VA_ARGS__);
#define PrtExp(_Exp)  cerr<< #_Exp <<" = "<< (_Exp)
#define PrtExpN(_Exp)  cerr<< #_Exp <<" = "<< (_Exp) <<"\n"

#define SINT(n) scanf("%d",&n);
#define SINT2(n,m) scanf("%d %d",&n,&m);
#define SINT3(n,m,o) scanf("%d %d %d",&n,&m,&o);
#define SINT4(n,m,o,p) scanf("%d %d %d %d",&n,&m,&o,&p);
#define SINT5(n,m,o,p,q) scanf("%d %d %d %d %d",&n,&m,&o,&p,&q);
//#define SLL(n) scanf("%I64d",&n);
#define SLL(n) scanf("%lld",&n);
#define SLL2(n,m) scanf("%lld %lld",&n,&m);
#define SLL3(n,m,o) scanf("%lld %lld %lld",&n,&m,&o);
#define SST(s) scanf("%s",s);
#define SCH(c) scanf("%c",&c);

#define GC() getchar();

#define PINT(n) printf("%d",(int)(n));
#define PINT2(n,m) printf("%d %d",(int)(n),(int)(m));
#define PINT3(n,m,l) printf("%d %d %d",(int)(n),(int)(m),(int)(l));
//#define PLL(n) printf("%I64d",(long long)(n));
#define PLL(n) printf("%lld",(long long)(n));
#define PST(s) printf("%s",(s));
#define PCH(s) printf("%c",(s));

#define PINTN(n) printf("%d\n",(int)(n));
#define PINT2N(n,m) printf("%d %d\n",(int)(n),(int)(m));
#define PINT3N(n,m,l) printf("%d %d %d\n",(int)(n),(int)(m),(int)(l));
//#define PLLN(n) printf("%I64d\n",(long long)(n));
#define PLLN(n) printf("%lld\n",(long long)(n));
#define PSTN(s) printf("%s\n",(s));
#define PCHN(s) printf("%c\n",(s));

#define PSP() printf(" ");
#define PN() printf("\n");

#define PC(c) putchar(c);
#define CSP (' ')
#define SN ("\n")

#define rep(i,a) for(int i=0;i<a;i++)
#define reP(i,a) for(int i=0;i<=a;i++)
#define Rep(i,a) for(int i=a-1;i>=0;i--)
#define ReP(i,a) for(int i=a;i>=0;i--)

#define rEp(i,a) for(i=0;i<a;i++)
#define rEP(i,a) for(i=0;i<=a;i++)
#define REp(i,a) for(i=a-1;i>=0;i--)
#define REP(i,a) for(i=a;i>=0;i--)

#define repft(i,a,b) for(i=a;i<b;i++)
#define repfT(i,a,b) for(i=a;i<=b;i++)
#define Repft(i,a,b) for(i=a-1;i>=b;i--)
#define RepfT(i,a,b) for(i=a;i>=b;i--)

#define foreach(a,it) for(auto it = a.begin(); it != a.end(); ++it)

#define FILL(a,v) fill(begin(a),end(a), v)
#define FILL0(a) memset(a,0,sizeof(a))
#define FILL1(a) memset(a,-1,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> Pi;
typedef pair<ll, ll>   Pll;


const int INF = 0x1f1f1f1f;//522,133,279
const ll INFLL = 0x1f1f1f1f1f1f1f1fLL;//2,242,545,357,980,376,863

template <class A, class B> inline ostream& operator<<(ostream& st, const pair<A, B>& P) { return st << "(" << P.first << "," << P.second << ")"; };
template <class A, class B> inline pair<A, B> operator+(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first + Q.first, P.second + Q.second); };
template <class A, class B> inline pair<A, B> operator-(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first - Q.first, P.second - Q.second); };

ll bitcount(ll bits) {
	bits = (bits & 0x5555555555555555) + (bits >> 1 & 0x5555555555555555);
	bits = (bits & 0x3333333333333333) + (bits >> 2 & 0x3333333333333333);
	bits = (bits & 0x0f0f0f0f0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f0f0f0f0f);
	bits = (bits & 0x00ff00ff00ff00ff) + (bits >> 8 & 0x00ff00ff00ff00ff);
	bits = (bits & 0x0000ffff0000ffff) + (bits >> 16 & 0x0000ffff0000ffff);
	return (bits & 0x00000000ffffffff) + (bits >> 32 & 0x00000000ffffffff);
}




vector<int> a[100000];
vector<int> b[100000];


int main() {
	int n, m;
	
	cin >> n >>  m;

	rep(i, n) {
		int x;
		cin >> x;
		a[x%m].push_back(x);
	}


	int i;
	repft(i, 1, m) {
		sort(a[i].begin(), a[i].end());

		rep(j, (int)(a[i].size())-1) {
			if (a[i][j] == a[i][j + 1]) {
				b[i].push_back(a[i][j]);
				b[i].push_back(a[i][j]);
				a[i][j] = a[i][j + 1] = -1;
				j++;
			}
		}
		for (auto&x : a[i]) {
			if (x >= 0) {
				b[i].push_back(x);
			}
		}
	}
	
	int ret = 0;

	ret += a[0].size() / 2;

	//cerr << " # " << ret << endl;

	if (m % 2 == 0) {
		ret += b[m / 2].size() / 2;
		b[m / 2].clear();
	}

	//cerr << " # " << ret << endl;

	
	for (i = 0; i * 2 < m; ++i) {
		int I = m - i;
		while (!b[i].empty() && !b[I].empty()) {
			ret++;
			b[i].pop_back();
			b[I].pop_back();
		}
	}


	repft(i, 1, m) {
		rep(j, ((int)(b[i].size())) - 1) {
			//cerr << i << " "<<j << endl;
			if (b[i][j] == b[i][j + 1]) {
				ret++;
				j++;
			}
		}
	}

	cout << ret << endl;
}

Submission Info

Judge Result