I need help implementing a few functions in c++. Any help would be appreciated

1. a function void PairsAddUpToK(int a[], int a_len, int k) that finds all pairs of numbers in an array that add up to a given number k

2. A function void TriplesAddUpToK(int a[], int a_len, int k) that finds all sets of three numbers in an array that ad up to a given number k

3. A function void SubsetsAddUpToK((int a[], int a_len, int k) that finds all possible subsets of numbers that add up to k