Submission #992665

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define fo(i,a,b) for(int i=(a);i<(b);i++)
#define MOD 1000000007
#define MP make_pair
#define PB push_back
typedef long long ll;

int N, M, cnt[100100], g[100100], odd[100100], ans;
vector<int> v[100100], n[100100];

int main () {
        scanf("%d %d", &N, &M);
        fo(i, 0, N) {
                int x;
                scanf("%d", &x);
                cnt[x%M]++;
                v[x%M].PB(x);
        }
        fo(i, 0, M) {
                sort(v[i].begin(), v[i].end());
                fo(j, 0, (int) v[i].size()) {
                        if (!j || v[i][j-1] != v[i][j]) {
                                int x = j; while (x+1 < (int) v[i].size() && v[i][x+1] == v[i][j]) x++;
                                n[i].PB(x-j+1);
                                if (n[i].back()&1) odd[i]++, g[i] += x-j;
                                else g[i] += x-j+1;
                        }
                }
        }

        ans = cnt[0]/2;
        if (M%2 == 0) ans += cnt[M/2]/2;

        for (int i = 1; i < M-i; i++) {
                int a = i, b = M-i;
                if (odd[a] > odd[b]) swap(a, b);
                ans += odd[a], odd[b] -= odd[a], odd[a] = 0;
                while (odd[b] >= 2 && g[a] >= 2) odd[b] -= 2, g[a] -= 2, ans += 2;
                ans += g[a]/2 + g[b]/2;
        }

        printf("%d\n", ans);
        return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:13:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &N, &M);
                               ^
./Main.cpp:16:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
                 scanf("%d", &x);
                                ^

Judge Result