Java: Coin Change

Problem Statement:

Given an integer array of coins[ ] of size N representing different types of currency and an

integer sum, The task is to find the number of ways to make sum by using different

combinations from coins[].

Note: Assume that you have an infinite supply of each type of coin.

Input:

sum = 4, coins[] = {1,2,3},

4
there are four solutions: {1, 1, 1, 1}, {1, 1, 2}, {2, 2}, {1, 3}.