Coin Change 2 · LeetCode

Description

You are given coins of different denominations and a total amount of money. Write a function to compute the number of combinations that make up that amount. You may assume that you have infinite number of each kind of coin.

Example 1:

Input: amount = 5, coins = [1, 2, 5]
Output: 4
Explanation: there are four ways to make up the amount:
5=5
5=2+2+1
5=2+1+1+1
5=1+1+1+1+1

Example 2:

Input: amount = 3, coins = [2]
Output: 0
Explanation: the amount of 3 cannot be made up just with coins of 2.

Example 3:

Input: amount = 10, coins = [10] 
Output: 1

Note:

You can assume that

0 <= amount <= 5000
1 <= coin <= 5000
the number of coins is less than 500
the answer is guaranteed to fit into signed 32-bit integer

Solution(javascript)

// Algorithm explanation: https://youtu.be/jaNZ83Q3QGc

/**
 * @param {number} amount
 * @param {number[]} coins
 * @return {number}
 */
var change = function(amount, coins) {
    const arr = Array(amount+1).fill(0);
    arr[0]=1;
    
    for(let coin of coins) {
        for(let i = 0; i <= amount; i++){
            const dif = i - coin;
            if(dif >= 0){
                arr[i] += arr[i-coin];
            }
        }
    }
    
    return arr[amount];
};