Submission #67704

#	Time	Username	Problem	Language	Result	Execution time	Memory
67704		tatatan	XOR Sum (info1cup17_xorsum)	C++11	45 / 100	1651 ms	34080 KiB

xorsum

#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define LL long long
#define st first
#define nd second
#define endl '\n'
using namespace std;

const int MAXN=1000005;
int n,a[MAXN],b[MAXN],ans;

int main() {

	scanf("%d",&n);
	for(int i=0;i<n;++i)
		scanf("%d",&a[i]);
	vector<pii> v;
	for(int i=0;i<n;++i)
		v.pb(mp(0,i));
	for(int i=0;i<30;++i) {
		int xo=(1<<(i+1))-1,t1,t2,t3;
		LL cnt=0;
		vector<pii> av,bv;
		for(int j=0;j<n;++j)
			if((1<<i)&(a[v[j].nd]))
				bv.pb(mp(v[j].st+(1<<i),v[j].nd));
			else av.pb(v[j]);
		v.clear();
		for(int j=0;j<av.size();++j)
			v.pb(av[j]);
		for(int j=0;j<bv.size();++j)
			v.pb(bv[j]);
		for(int j=0;j<n;++j) 
			b[j]=v[j].st;
		sort(b,b+n);
		t1=t2=t3=n;
		for(int j=0;j<n;++j) {
			while(t1&&b[t1-1]>=(1<<i)-b[j])
				--t1;
			while(t2&&b[t2-1]>=(1<<(i+1))-b[j])
				--t2;
			while(t3&&b[t3-1]>=(1<<(i+1))+(1<<i)-b[j])
				--t3;
			cnt+=(n-t1-(t3-t2));
		}
		for(int j=0;j<n;++j)
			if((b[j]*2)&(1<<i)) --cnt;
		cnt/=2;		
		for(int j=0;j<n;++j)
			if((b[j]*2)&(1<<i)) ++cnt;		
		if(cnt&1) ans+=(1<<i);
	}
	printf("%d\n",ans);

}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:31:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<av.size();++j)
               ~^~~~~~~~~~
xorsum.cpp:33:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<bv.size();++j)
               ~^~~~~~~~~~
xorsum.cpp:23:7: warning: unused variable 'xo' [-Wunused-variable]
   int xo=(1<<(i+1))-1,t1,t2,t3;
       ^~
xorsum.cpp:16:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
xorsum.cpp:18:8: 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: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 38 / 38
• Subtask 5: 0 / 23