[BZOJ1660][Usaco2006 Nov]Bad Hair Day 乱发节

#include <cstdio>
const int maxn = 80000 + 10;
int h[maxn], sta[maxn], top = 0;
int main(){
    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) scanf("%d", h + i);
    h[n + 1] = 1 << 30;
    sta[top = 1] = n + 1;
    long long ans = 0;
    for(int i = n; i; i--){
        while(top && h[i] > h[sta[top]]) top--;
        ans += sta[top] - i - 1;
        sta[++top] = i;
    }
    printf("%lld\n", ans);
    return 0;
}