I think:
给出k(4≤k≤5000)个互不相同的整数组成的序列Ni,判断是否存在4个整数Np、Nq、Nr和Ns(1≤p<q<r<s≤k),使得Nq>Ns>Np>Nr或者Nq<Ns<Np<Nr。
p q r s
6 8 5 7 -- Nq>Ns>Np>Nr
7 5 8 6 -- Nq<Ns<Np<Nr
#include <stdio.h>
int main(void)
{int n,t,i,numarr[10000],tem,j,k,flag;while(scanf("%d",&n)!=EOF){while(n--){flag=0;scanf("%d",&t);for(i=0; i<t; i++){scanf("%d",&numarr[i]);}for(i=0; i<t; i++){tem=numarr[i];if(numarr[i+1]>tem){for(j=i+2; j<t; j++){if(numarr[j]<tem){for(k=j+1; k<t; k++){if(numarr[k]>tem&&numarr[k]<numarr[i+1])flag=1;}}}}if(flag==1)break;}for(i=0; i<t; i++){if(flag==1)break;tem=numarr[i];if(numarr[i+1]<tem){for(j=i+2; j<t; j++){if(numarr[j]>tem){for(k=j+1; k<t; k++){if(numarr[k]<tem&&numarr[k]>numarr[i+1])flag=1;}}}}}if(flag)printf("YES\n");else printf("NO\n");}}return 0;
}