【poj 3250】 Bad Hair Day

单调栈

#include <iostream>#include <cstdio>using namespace std;long long n, a1[80010], p1[80010], p, ans;int main(){scanf("%lld", &n);for(int i = 1; i <= n; i ++) scanf("%lld", &a1[i]);a1[++n] = 1e9+10;for(int i = 1; i <= n; i ++){while(p && a1[p1[p]] <= a1[i]) ans += (i-p1[p]-1), p --;p1[++p] =  i;}printf("%lld", ans);return 0;}