蓝桥--鸡哥的购物挑战OJ(4169)

#include <iostream>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e5 + 10;
LL w[N];
LL sum[N];
int n;
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> w[i];
    sort (w + 1, w + n + 1);
    int num = 0;
    for (int i = 1; i <= n; i++)
        if (w[i] > 0)   num++;
    for (int i = 1; i <= n; i++)   sum[i] = sum[i - 1] + w[i];
    //防止都是大于0的数，特判一下
    if (num == n && num & 1)
    {
        cout << sum[n] - w[1];
        return 0;
    }
    LL res = 0;
    if (num & 1)
    {
        int last = w[n - num + 1] + w[n - num];
        if (last >= 0)
            res = sum[n] - sum[n - num - 1];
        else 
            res = sum[n] - sum[n - num + 1];
    }
    else 
        res = sum[n] - sum[n - num];
    cout << res;
    return  0;
}