Submission #68034

#	Time	Username	Problem	Language	Result	Execution time	Memory
68034		top34051	XOR Sum (info1cup17_xorsum)	C++17	100 / 100	1238 ms	36060 KiB

xorsum

#include<bits/stdc++.h>
using namespace std;

#define X first
#define Y second
const int maxn = 1e6 + 5;
const int mlog = 29;

int n;
int a[maxn];

int main() {
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]);

	int ans = 0;

	vector<pair<int,int>> b[2];
	for(int i=1;i<=n;i++) b[0].push_back({0,a[i]});

	for(int i=0;i<=mlog;i++) {
		int pw = (1<<i);

//		printf("pw = %d\n",pw);

		vector<pair<int,int>> tmp[2];
		for(auto t : b[0]) {
            int x = t.second;
            tmp[(x/pw)%2].push_back({x%pw,x});
		}
		for(auto t : b[1]) {
            int x = t.second;
            tmp[(x/pw)%2].push_back({x%pw,x});
		}
		b[0] = tmp[0];
		b[1] = tmp[1];
		int sz0 = b[0].size();
		int sz1 = b[1].size();

//        printf("\t");
//		for(auto t : b[0]) printf("%d ",t);
//		printf("\n");
//        printf("\t");
//		for(auto t : b[1]) printf("%d ",t);
//		printf("\n");

		long long cnt1 = 0, cnt2 = 0, cnt3 = 0;

		//tx = 0 ty = 0
		//2^i <= b[x] + b[y] (< 2^(i+1))
		for(int x=0,y=sz0;x<sz0;++x) {
			while(y-1 >= 0 && pw <= b[0][x].X + b[0][y-1].X) --y;
			cnt1 += sz0-y;
		}
		for(auto t : b[0]) if(pw <= t.X*2) cnt1++;
		cnt1 /= 2;

		//tx = 0 ty = 1
		//b[x] + b[y] < 2^i
		for(int x=sz0-1,y=-1;x>=0;--x) {
			while(y+1 < sz1 && b[0][x].X + b[1][y+1].X < pw) ++y;
			cnt2 += y+1;
		}

		//tx = 1 ty = 1
		//2^i <= b[x] + b[y] (< 2^(i+1))
		for(int x=0,y=sz1;x<sz1;++x) {
			while(y-1 >= 0 && pw <= b[1][x].X + b[1][y-1].X) --y;
			cnt3 += sz1-y;
		}
		for(auto t : b[1]) if(pw <= t.X*2) cnt3++;
		cnt3 /= 2;

		if((cnt1+cnt2+cnt3)&1) ans += pw;
	}

	printf("%d",ans);
}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:13:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
xorsum.cpp:14:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1;i<=n;i++) scanf("%d",&a[i]);
                        ~~~~~^~~~~~~~~~~~

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