Submission #45673

#	Time	Username	Problem	Language	Result	Execution time	Memory
45673		aome	XOR Sum (info1cup17_xorsum)	C++17	100 / 100	1317 ms	56396 KiB

xorsum

#include <bits/stdc++.h>
 
using namespace std;
 
const int N = 1000005;
 
int n;
int res;
int a[N];
int b[N];
bool p[35][N];
int arr[N];
int f[2][N];
int buf[2][N];
 
int main() {
	scanf("%d", &n);
	for (int i = 0; i < n; ++i) {
		scanf("%d", &a[i]);
		for (int j = 0; j < 30; ++j) {
			p[j][i] = a[i] >> j & 1;
		}
	}
	for (int i = 0; i < n; ++i) arr[i] = i;
	for (int i = 0; i <= 30; ++i) {
		// cout << "#\n";
		// for (int j = 0; j < n; ++j) cout << arr[j] << ' ' << b[arr[j]] << '\n';
 
		for (int j = n - 1; j >= 0; --j) {
			f[0][j] = f[0][j + 1], f[1][j] = f[1][j + 1];
			f[p[i][arr[j]]][j]++;
		}
		int cur = 0, ptr = n;
		int cnt[2];
		cnt[0] = cnt[1] = 0;
		for (int j = 0; j < n; ++j) {
			if (ptr < j) {
				cnt[p[i][arr[ptr]]]--, ptr++;
			}
			while (ptr > j && b[arr[ptr - 1]] + b[arr[j]] >= (1 << i)) {
				ptr--, cnt[p[i][arr[ptr]]]++;
			}
			int cnt2[2];
			cnt2[0] = f[0][j] - cnt[0];
			cnt2[1] = f[1][j] - cnt[1];
			cur ^= cnt[p[i][arr[j]]] & 1;
			cur ^= cnt2[p[i][arr[j]] ^ 1] & 1;
		}
		res += cur << i;
		if (i == 30) break;
		int sz[2];
		sz[0] = sz[1] = 0;
		for (int j = 0; j < n; ++j) {
			b[j] += p[i][j] << i;
		}
		for (int j = 0; j < n; ++j) {
			bool x = p[i][arr[j]]; buf[x][sz[x]++] = arr[j];
		}
		for (int j = 0; j < sz[0]; ++j) {
			arr[j] = buf[0][j];
		}
		for (int j = 0; j < sz[1]; ++j) {
			arr[j + sz[0]] = buf[1][j];
		}
	}
	cout << res;
}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:17:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
xorsum.cpp:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &a[i]);
   ~~~~~^~~~~~~~~~~~~

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