Submission #992254

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Source Code Expand

#include <iostream>
#include <fstream>
#include <sstream>

#include <vector>
#include <set>
#include <bitset>
#include <map>
#include <deque>
#include <string>

#include <algorithm>
#include <numeric>

#include <cstdio>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cmath>

#define pb push_back
#define pbk pop_back
#define mp make_pair
#define fs first
#define sc second
#define all(x) (x).begin(), (x).end()
#define foreach(i, a) for (__typeof((a).begin()) i = (a).begin(); i != (a).end(); ++i)
#define len(a) ((int) (a).size())

#ifdef CUTEBMAING
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif

using namespace std;

typedef long long int64;
typedef long double ld;
typedef unsigned long long lint;

const int inf = (1 << 30) - 1;
const int64 linf = (1ll << 62) - 1;
const int N = 1e6 + 100;

vector<int> a[N];

inline int match(vector<int> a, vector<int> b) {
    if (len(a) < len(b)) {
        swap(a, b);
    }
    int can = len(b);
    int left = (len(a) - len(b)) / 2;
    map<int, int> c;
    for (int i : a) {
        c[i]++;
    }
    for (auto i : c) {
        int cnt = min(left, i.sc / 2);
        left -= cnt;
        can += cnt;
    }
    return can;
}

int main() {
#ifdef XCODE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int n, m; cin >> n >> m;
    for (int i = 0; i < n; i++) {
        int x; scanf("%d", &x);
        a[x % m].pb(x);
    }
    for (int i = 0; i < m; i++) {
        sort(all(a[i]));
    }
    int ans = 0;
    for (int i = 0; i < m && i <= m - i; i++) {
        if ((2 * i) % m == 0 || i == 0) {
            ans += len(a[i]) / 2;
        } else {
            ans += match(a[i], a[m - i]);
        }
    }
    cout << ans << endl;
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:74:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         int x; scanf("%d", &x);
                               ^

Judge Result