Submission #3239652

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Source Code Expand

#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<map>
#include<set>
#include<bitset>
#define INF 1<<29
#define LL long long
#define WY()(putchar('Y'),putchar('e'),putchar('s'),putchar('\n'))
#define WN()(putchar('N'),putchar('o'),putchar('\n'))
#define Max(x,y)(x>y? x:y)
#define Min(x,y)(x<y? x:y)
#define ek()(putchar('\n'))
#define sk()(putchar(' '))
#define MAXN 405
#define MAXM 100005
using namespace std;
inline int Read(){
	int X=0,flag=1;char ch=0;
	while (ch<'0'||ch>'9'){
		if (ch=='-') flag=-1;
		ch=getchar();
	}
	while (ch>='0'&&ch<='9')
	  X=(X<<1)+(X<<3)+ch-48,ch=getchar();
	return X*flag;
}
inline void Write(int x){
	if (x<0) x=-x,putchar('-');
	if (x>9) Write(x/10);
	putchar(x%10+48);
}
int n,m;
bitset<MAXN> alive[MAXN];
int x[MAXM],y[MAXM];
bool ok[MAXN];
int main(){
	n=Read(),m=Read();
	for (int i=1;i<=m;i++) x[i]=Read(),y[i]=Read();
	for (int i=1;i<=n;i++) ok[i]=alive[i][i]=1;
	for (int i=1;i<=n;i++)
	  for (int j=m;j;j--){
	  	int xx=x[j],yy=y[j];
	  	if (!alive[i][xx]&&!alive[i][yy]) continue;
	  	if (alive[i][xx]&&alive[i][yy]){
	  		ok[i]=0;
	  		break;
		}
		alive[i][xx]=alive[i][yy]=1;
	  }
	int ans=0;
	for (int i=1;i<=n;i++)
	  for (int j=i+1;j<=n;j++)
	    if (ok[i]&&ok[j]&&(alive[i]&alive[j]).none())
	      ans++;
	Write(ans);ek();
    return 0;
}

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