Submission #1139716

#	Time	Username	Problem	Language	Result	Execution time	Memory
1139716		Kerim	XOR Sum (info1cup17_xorsum)	C++20	100 / 100	404 ms	19604 KiB

xorsum

#include "bits/stdc++.h"
#define ff first
#define ss second
#define ll long long
using namespace std;
const int N = 1e6+5;
int a[N];
vector<int> val[2], tmp[2];
ll uly(vector<int> &A, vector<int> &B, int K){
    ll cnt = 0;
    int sz = (int)B.size() - 1;
    int p = sz;
    for (auto x: A){
        while (p >= 0 and x+B[p]>=K)
            p -= 1;
        cnt += sz - p;
    }
    return cnt;
}
ll kici(vector<int> &A, vector<int> &B, int K){
    return (ll)A.size()*(ll)B.size() - uly(A, B, K);
}
int main(){
    // freopen("file.in", "r", stdin);
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        scanf("%d", a+i);
    vector<pair<int,int> > tries{{0,0}, {1,1}, {0, 1}};
    int ans = 0;
    for (int k = 0; k < 30; k++){
        for (int j = 0; j < 2; j++)
            tmp[j].clear(), val[j].clear();

        for (int i = 0; i < n; i++){
            val[a[i]>>k&1].push_back(a[i]%(1<<k));
            tmp[a[i]>>k&1].push_back(a[i]);
        }

        int p = 0;
        for (auto y: tmp[0])
            a[p++] = y;
        for (auto y: tmp[1])
            a[p++] = y;

        int K = (1<<k);
        int n00 = uly(val[0], val[0], K); //p+q>=K
        int n11 = uly(val[1], val[1], K); //p+q>=K
        int n01 = kici(val[0], val[1], K); //p+q<K

        //remove duplicates
        for (auto A: val[0])
            n00 += (A+A >= K);
        n00 /= 2;

        //remove duplicates
        for (auto A: val[1])
            n11 += (A+A >= K);
        n11 /= 2;

        int cnt = n00 + n11 + n01;
        if (cnt&1)
            ans |= (1<<k);
    }
    printf("%d\n", ans);
}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:26:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   26 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
xorsum.cpp:28:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         scanf("%d", a+i);
      |         ~~~~~^~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 11 / 11
• Subtask 3: 21 / 21
• Subtask 4: 38 / 38
• Subtask 5: 23 / 23