Submission #2404

#	Time	Username	Problem	Language	Result	Execution time	Memory
2404		alephnull	지우개 (GA4_eraser)	C++98	100 / 100	40 ms	3192 KiB

eraser

#include <cstdio>
#include <algorithm>
#include <vector>

#define MOD 1000000007
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef vll::iterator vlli;
int main() {
	int n;scanf("%d",&n);
	vll a(n,0);
	for(int i=0;i<n;i++){
		long long tmp;
		scanf("%lld",&tmp);a[i]=tmp;
	}
	sort(a.begin(),a.end());
	vll psum(n,0);
	psum[0]=a[0];
	for(int i=1;i<n;i++)psum[i]=(psum[i-1]+a[i])%MOD;
	vll ppsum(n,0);
	for(int i=n-2;i>=0;i--){
		vlli hi= upper_bound(a.begin(),a.end(),a[i]);
		int idx=hi-a.begin();
		if(idx==n)ppsum[i]=ppsum[i+1];
		else{ppsum[i]=(ppsum[i+1]+(a[i]*((MOD+psum[n-1]-psum[idx-1])%MOD))%MOD)%MOD;}
		//printf("%lld %lld ",a[i],psum[n-1]-psum[idx-1]);
	}
	ll ans=0;
	for(int i=0;i<n;i++){
		vlli hi= upper_bound(a.begin(),a.end(),a[i]);
		int idx=hi-a.begin();
		//printf("%d\n",idx);
		if(idx==n)continue;
		ans=(ans+(a[i]*ppsum[idx])%MOD)%MOD;

	}
	//for(int i=0;i<n;i++)printf("%lld ",ppsum[i]);
	printf("%lld\n",ans);
}

• Subtask 1: 6 / 6
• Subtask 2: 7 / 7
• Subtask 3: 16 / 16
• Subtask 4: 17 / 17
• Subtask 5: 26 / 26
• Subtask 6: 28 / 28