How can I manipulate an array to make the largest number?

Question

Say you have an array of positive integers, manipulate them so that the concatenation of the integers of the resultant array is the largest number possible. Ex: {9,1,95,17,5}, r

Answer 1

Here is the implementation in c++

#include 
#include 

using namespace std;

/**
    a = 123
    b = 15
    v1 = 12315
    v2 = 15123
    return (v2 - v1) to make the function sort in descending order
*/
int compare_concatenated_ints(const void *arg1, const void *arg2)
{
    int v1 = *(int*) arg1;
    int v2 = *(int*) arg2;

    stringstream s1, s2;
    s1 << v1 << v2;
    s2 << v2 << v1;

    s1 >> v1;
    s2 >> v2;

    return (v2 - v1);
}

void print_array(int arr[], int count)
{
    for (int i = 0; i < count; ++i){
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main()
{
    int arr[] = {4, 0, 94, 9, 14, 0, 1};    
    int count = sizeof(arr)/sizeof(arr[0]);

    printf("BEFORE\n");
    print_array(arr, count);

    std::qsort(arr, count, sizeof(int), compare_concatenated_ints);

    printf("AFTER\n");
    print_array(arr, count);
}