【洛谷P2866】Bad Hair Day

单调栈版子

 #include<cstdio>
 #include<cstring>
 using namespace std;
 const int N=;
 int n,a,top=,zh[N];
 int read(){
     int sum=;
     char ch=getchar();
     while (ch<''||ch>'')
         ch=getchar();
     while (ch>=''&&ch<=''){
         sum=sum*+ch-'';
         ch=getchar();
     }
     return sum;
 }
 int main(){
     long long ans=;
     scanf("%d",&n);
     for (int i=;i<=n;i++){
         a=read();
         while (a>=zh[top]&&top) top--;
         ans+=top;
         zh[++top]=a;
     }
     printf("%lld",ans);
     return ;
 }