#include <algorithm>
#include <iostream>
#include <functional>
#include <map>
 
int main()
{
    int numbers[] = {18, 12, 4, 5};
    char signs[] = {'+', '-', '/', '*'};
    std::map<char, std::function<int(int, int)>> m = {
        {'+', [](int a, int b){ return a + b; }},
        {'-', [](int a, int b){ return a - b; }},
        {'/', [](int a, int b){ return a / b; }},
        {'*', [](int a, int b){ return a * b; }},
    };
 
    std::sort(std::begin(signs), std::end(signs));
 
    do {
        int res = m[signs[2]](m[signs[1]](m[signs[0]](numbers[0], numbers[1]), numbers[2]), numbers[3]);
 
        std::cout << numbers[0] << signs[0] << numbers[1] << signs[1]
            << numbers[2] << signs[2] << numbers[3] << " = " << res << std::endl;
 
    } while (std::next_permutation(std::begin(signs), std::end(signs)));
    return 0;
}
 

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