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Solution Review: Create an Amount

Solution Review: Create an Amount

This lesson will discuss the two possible solutions to the challenge in the previous lesson: recursive and dynamic.

We'll cover the following...

Solution: recursive #

Let’s start by discussing the recursive solution to this problem.

Javascript (babel-node)
function returnWays(coins, numOfCoins,amount) {
    
    if(amount === 0) return 1; // only one way to return zero amount
    
    if(amount < 0) return 0; // No solution exists for negative amount
    
    if(numOfCoins < 0 && amount > 0) return 0; // If no coins left
    
    return returnWays(coins, numOfCoins, amount - coins[numOfCoins]) + 
           returnWays(coins, numOfCoins - 1, amount);
}
var coins = [1, 2, 3];
var amount = 4;
console.log(returnWays(coins,coins.length-1,amount));

Explanation #

We start with a big problem. Given an amount and an array of coins, we have to find the number of ways to return that amount using the coins from the array.

In a recursive solution, we split the ...