[c++] Creating all possible k combinations of n items in C++

I thought my simple "all possible combination generator" might help someone, i think its a really good example for building something bigger and better

you can change N (characters) to any you like by just removing/adding from string array (you can change it to int as well). Current amount of characters is 36

you can also change K (size of the generated combinations) by just adding more loops, for each element, there must be one extra loop. Current size is 4

#include<iostream>

using namespace std;

int main() {
string num[] = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z" };

for (int i1 = 0; i1 < sizeof(num)/sizeof(string); i1++) {
    for (int i2 = 0; i2 < sizeof(num)/sizeof(string); i2++) {
        for (int i3 = 0; i3 < sizeof(num)/sizeof(string); i3++) {
            for (int i4 = 0; i4 < sizeof(num)/sizeof(string); i4++) {
                cout << num[i1] << num[i2] << num[i3] << num[i4] << endl;
            }
        }
    }
}}

Result

0: A A A
1: B A A
2: C A A
3: A B A
4: B B A
5: C B A
6: A C A
7: B C A
8: C C A
9: A A B
...

just keep in mind that the amount of combinations can be ridicules.

--UPDATE--

a better way to generate all possible combinations would be with this code, which can be easily adjusted and configured in the "variables" section of the code.

#include<iostream>
#include<math.h>

int main() {
    //VARIABLES
    char chars[] = { 'A', 'B', 'C' };
    int password[4]{0};

    //SIZES OF VERIABLES
    int chars_length = sizeof(chars) / sizeof(char);
    int password_length = sizeof(password) / sizeof(int);

    //CYCKLE TROUGH ALL OF THE COMBINATIONS
    for (int i = 0; i < pow(chars_length, password_length); i++){
       
        //CYCKLE TROUGH ALL OF THE VERIABLES IN ARRAY
        for (int i2 = 0; i2 < password_length; i2++) {
            //IF VERIABLE IN "PASSWORD" ARRAY IS THE LAST VERIABLE IN CHAR "CHARS" ARRRAY
            if (password[i2] == chars_length) {
                //THEN INCREMENT THE NEXT VERIABLE IN "PASSWORD" ARRAY
                password[i2 + 1]++;
                //AND RESET THE VERIABLE BACK TO ZERO
                password[i2] = 0;
            }}

        //PRINT OUT FIRST COMBINATION
        std::cout << i << ": ";
        for (int i2 = 0; i2 < password_length; i2++) {
            std::cout << chars[password[i2]] << " ";
        }
        std::cout << "\n";

        //INCREMENT THE FIRST VERIABLE IN ARRAY
        password[0]++;
    }}

    

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