CF-358A

类似区域的交并。

#include<iostream>#include<cstdio>#include<cstring>typedef __int64 LL;using namespace std ;int main(){    int n;    LL a[1005];    LL t1,t2;    while(scanf("%d",&n)!=EOF){for(int i=0;i<n;i++){scanf("%I64d",&a[i]);}bool flag=0;for(int i=0;i<n-2;i++){for(int j=i+2;j<n-1;j++){t1=(a[j]-a[i])*(a[j]-a[i+1]);t2=(a[j+1]-a[i])*(a[j+1]-a[i+1]);if(t1<0&&t2>0||t1>0&&t2<0){flag=1;break;}}if(flag) break;}if(flag) puts("yes");else puts("no");    } return 0 ;}