洛谷P1419寻找段落

题目

单调队列+前缀和

#include <bits/stdc++.h>
#define N 101001
using namespace std;
int n, s, t; int data[N];
double ans, temp[N], sum[N], l = -10000, r = 10000;
bool check(double a)
{
     deque <int> q;
    memset(sum, 0, sizeof(sum));
    for (int i = 1; i <= n; i++)
        temp[i] = (double) data[i] - a;
    sum[0] = 0;
    for (int i = 1; i <= n; i++)
        sum[i] = sum[i - 1] + temp[i];
    for (int i = 1; i <= n; i++)
    {                   
        if (i >= s) 
        {                   
            while (q.size() && sum[i - s] < sum[q.back()])
                q.pop_back();   
            q.push_back(i - s);
        }        
        if (q.size() && q.front() < i - t) 
        q.pop_front();
        if (q.size() && sum[i] >= sum[q.front()])    
            return true;
    }            
    return false;
}                
int main()       
{                
    scanf("%d%d%d", &n, &s, &t);
    for (int i = 1; i <= n; i++) scanf("%d", &data[i]);
    while (r - l > 0.00001)
    {            
        double mid = (l + r) / 2;
        if (check(mid))
        ans = l = mid;
        else     
        r = mid; 
    }
//  printf("%d", check(2));
    printf("%.3lf\n", ans);
    return 0;   
}