poj1701

简单题，推公式

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 10005

int n, u, d;
long long sum[maxn], f[maxn], extraup[maxn], extradown[maxn];
long long down[maxn], up[maxn];

void input()
{
    scanf("%d%d%d", &n, &u, &d);
    sum[0] = 0;
    for (int i = 1; i <= n; i++)
    {
        scanf("%lld", &f[i]);
        sum[i] = sum[i - 1] + f[i];
    }
    extradown[0] = 0;
    for (int i = 1; i <= n; i++)
        extradown[i] = extradown[i - 1] + sum[i];
    extraup[n + 1] = 0;
    for (int i = n; i >= 1; i--)
        extraup[i] = extraup[i + 1] + sum[n] - sum[i - 1];
}

void work()
{
    down[1] = 0;
    for (int i = 2; i <= n; i++)
        down[i] = sum[i - 2] * d + down[i - 1] + f[i - 1] * d + extradown[i - 2];
    up[n] = 0;
    for (int i = n - 1; i >= 1; i--)
        up[i] = (sum[n] - sum[i + 1]) * u + up[i + 1] + f[i + 1] * u + extraup[i + 2];
    long long temp = down[1] + up[1];
    int ans = 1;
    for (int i = 2; i <= n; i++)
        if (temp >= down[i] + up[i])
        {
            temp = down[i] + up[i];
            ans = i;
        }
    printf("%d\n", ans);
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    while (t--)
    {
        input();
        work();

    }
    return 0;
}