bzoj1660[Usaco2006 Nov]Bad Hair Day 乱发节*

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #define maxn 80100
 5 using namespace std;
 6 
 7 inline int read(){
 8     char ch=getchar(); int f=1,x=0;
 9     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}
10     while(ch>=‘0‘&&ch<=‘9‘)x=x*10+ch-‘0‘,ch=getchar();
11     return f*x;
12 }
13 int n,a[maxn],x[maxn],y[maxn],sz; long long ans;
14 int main(){
15     n=read(); for(int i=1;i<=n;i++)a[i]=read(); x[0]=0x3fffffff; y[0]=n+1; sz=0;
16     for(int i=n;i>=1;i--){while(a[i]>x[sz])sz--; ans+=(y[sz]-i-1); x[++sz]=a[i]; y[sz]=i;}
17     printf("%lld",ans); return 0;
18 }