P2866 糟糕的一天

 1 #include<cstdio>
 2 long long n,a[80010],stack[80010],top,ans=0;
 3 int main(){
 4     scanf("%lld",&n);
 5     for(long long i=1;i<=n;i++)
 6         scanf("%lld",&a[i]);
 7     a[n+1]=1<<30;
 8     for(long long i=1;i<=n+1;i++){
 9         while(top&&a[stack[top]]<=a[i]){
10             ans+=i-stack[top]-1;
11             top--;
12         }
13         stack[++top]=i;
14     }
15     printf("%lld",ans);
16     return 0;
17 }