單調棧-POJ 2796 Feel Good

POJ 2796 Feel Good

題目意思: \(\displaystyle \sum^j_{y=i}X_y, (1 \leq i\leq j \leq N）* min(X_{i}|1 \leq i \leq N)\)

PS:這題要多組讀入,C++ cout cin記得優化

#include <iostream>
#include <stack>
using namespace std;
typedef long long int ll;

const int MAXN = 1e6 + 7;
ll height[MAXN],sum[MAXN];
int Left,Right;
int n;

ll solve(){
    ll ans = 0;
    stack<int> s;
    height[n+1] = -1;
    Left = Right = 1;
    for(int i=1;i<=n+1;i++){
        while(!s.empty() && height[s.top()] > height[i]){
            int cur = s.top();
            s.pop();
            int _left = (s.empty()?1:s.top()+1);
            int _right = i-1;
            ll tmp = height[cur]*(sum[_right]-sum[_left-1]);
            if(tmp > ans){
                ans = tmp;
                Left = _left;
                Right = _right;
            }
        }
        s.push(i);
    }
    return ans;
}

int main(){
    while(~scanf("%d",&n)){
        sum[0] = 0;
        for(int i=1;i<=n;i++) {
            scanf("%lld",&height[i]);
            sum[i] = sum[i-1] + height[i];
        }
        printf("%lld\n",solve());
        printf("%d %d\n",Left,Right);   
    }
    return 0;
}