Blue Bridge Cup ADV-15 algorithm to increase the maximum product

Algorithm to increase the maximum product  

Time limit: 1.0s Memory Limit: 512.0MB

 

Problem Description

　　For the number n, the number removed from m, how to take the product so that the maximum number m of it?

 

Input Format

　　The first line number data representing a number of sets
　　of input data each of 2 lines:
　　Line 1 shows the total number and the number n of the number m of the number to be taken, 1 <= n <= m <= 15,
　　this in turn gives the second row of n numbers, wherein each number range satisfying: a [i] is the absolute value of 4 or less.

 

Output Format

　　Each data output line 1, the largest product.

 

Sample input

1
5 5
1 2 3 4 2

 

Sample Output

48

 

#include <cstdio>
#include <climits>
#include <vector>

using namespace std;

int n, m;
int a[20];
int max_prod;
vector<int> chosen_idx;

void find_max_prod(int current_idx, int num_chosen)
{
    if (num_chosen == m)
    {
        int prod = 1;
        for (int i = 0; i < chosen_idx.size(); ++i)
            prod *= a[chosen_idx[i]];
        if (prod > max_prod)
            max_prod = prod;
    }
    else if (current_idx >= n)
        return;
    else
    {
        chosen_idx.push_back(current_idx);
        find_max_prod(current_idx + 1, num_chosen + 1);
        chosen_idx.pop_back();
        find_max_prod(current_idx + 1, num_chosen);
    }
}

int main()
{
    int T;
    scanf("%d", &T);

    while (T--)
    {
        scanf("%d %d", &n, &m);
        for (int i = 0; i < n; ++i)
            scanf("%d", &a[i]);

        max_prod = INT_MIN;
        chosen_idx.clear();
        find_max_prod(0, 0);
        printf("%d\n", max_prod);
    }

    return 0;
}