Print all combinations of size r from an array of size n

Question

I want to solve the following problem: given an array of size n, print all combinations of size r. As far as I know combination means that the order does not matter, ie {1, 2} is the same as {2, 1} so we have to deal with repetitions. I tried to solve the problem recursively, but I print the same combination several times. This is my code:

//main method
public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4};
        int r = 3;
        permute(arr, r);
}

//permute function
private static void permute(int[] arr, int r) {
        int[] res = new int[r];
        doPermute(arr, res, 0, 0, r);
}

//helper function
private static void doPermute(int[] arr, int[] res, int currIndex, int level, int r) {
        if(level == r){
            printArray(res);
            return;
        }
        for (int i = currIndex; i < arr.length; i++) {
            res[level] = arr[currIndex];
            doPermute(arr, res, currIndex+1, level+1, r);
            doPermute(arr, res, currIndex+1, level, r);
        }
    }

//print array function
private static void printArray(int[] res) {
        for (int i = 0; i < res.length; i++) {
            System.out.print(res[i] + " ");
        }
        System.out.println();
}

And this is part of my very long output:

1 2 3 
1 2 4 
1 2 3 
1 2 4 
1 3 4 
1 3 4 
1 2 3 
1 2 4 

The code produces all combinations, however with many repetitions. Any help will ge appreciated!

Answer 1

Sorry for my previous answer, I just realized that it was so dumb, that's why I tried somethings for you, try to take off the loop :

private static void doPermute(int[] arr, int[] res, int currIndex, int level, int r) {
    if(level == r){
        printArray(res);
        return;
    }
    if(currIndex<arr.length){
        res[level] = arr[currIndex];
        doPermute(arr, res, currIndex+1, level+1, r);
        doPermute(arr, res, currIndex+1, level, r);
    }
}