POJ 1701

/*
Every tenant went up N floors would make the dissatisfied degree rise N * a + 0.5 * N * (N - 1) degrees,
every tenant went down N floors would make the dissatisfied degree rise N * b + 0.5 * N * (N - 1) degrees. 

  △= Dp+1 – Dp
= ∑1=<i<=p Ki*(b+p-i)) - ∑p<i<=n Ki*(a+i-p-1)
=  ∑1=<i<=n Ki * i +(b+p)*∑1=<i<=p Ki   -     (a-p-1)∑p<i<=n Ki
*/

#include <iostream>
#define MAXN  10001
using namespace std;

__int64 _m[MAXN+1];
int k[MAXN+1];
__int64 p_2[MAXN+1];
__int64 p_3[MAXN+1];
int k_1[MAXN];
int k_2[MAXN];


int main()
{
    //freopen("acm.acm","r",stdin);
    int test;
    int n;
    int i;
    int j;
    int  p_1;
    int a;
    int b;
    scanf("%d",&test);
    while(test --)
    {
        scanf("%d",&n);
        scanf("%d",&a);
        scanf("%d",&b);
    
        for(i = 1; i <= n; ++ i)
        {
            scanf("%d",&k[i]);
        }

        for(i = 1; i <= n; ++ i)
        {
            k_1[i] = k_2[i] = k[i];
        }

        for(i = n-1; i >=1; -- i)
        {
            k_2[i] += k_2[i+1];
        }

        for(i = 2; i <= n; ++i)
        {
            k_1[i] += k_1[i-1];
        }

        p_1 = 0;
        for(i = 1; i <= n; ++ i)
        {
            p_1 += k[i]*i;
        }

        for(i = 1; i <= n; ++ i)
        {
            p_2[i] = (b + i)*k_1[i];
        }

        for(i = 1; i <= n; ++ i)
        {
            k_2[i] -= k[i];    
        }
                

        copy(k_2,k_2+n+1,p_3);
    
        for(i = 1; i <= n; ++ i)
        {
            p_3[i] *= (a-i-1);
        }
        _m[1] = 0;
        for(i = 2; i <= n; ++ i)
        {
            _m[1] += (i-1)*a+((i-1)*(i-2)/2);
        }

        for(i = 2; i <= n; ++ i)
        {
            _m[i] = _m[i-1] - p_1 + p_2[i-1] - p_3[i-1];
        }

        __int64 min = 999999999999999;

        int place;
    
        for(i = 1; i <= n; ++ i)
        {
            if(_m[i] < min)
            {
                min = _m[i];
                place = i;
            }
        }
        cout<<place<<endl;
    }
}

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