Coin Change

Coin Change dynamic programming

You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1.

Example 1:
coins = [1, 2, 5], amount = 11
return 3 (11 = 5 + 5 + 1)

Example 2:
coins = [2], amount = 3
return -1.

Note: You may assume that you have an infinite number of each kind of coin.

Coin Change Solution

class CoinChange {
    public int coinChange(int[] coins, int amount) {
        if(amount < 1) {
            return 0;
        }

        return coinChangeRecursive(coins, amount, new int[amount]);
    }

    public int coinChangeRecursive(int[] coins, int amount, int[] dp) {
        if(amount < 0) {
            return -1;
        }
        if(amount == 0) {
            return 0;
        }
        if(dp[amount - 1] != 0) {
            return dp[amount - 1];
        }

        int min = Integer.MAX_VALUE;
        for(int coin: coins) {
            int result = coinChangeRecursive(coins, amount - coin, dp);
            if(result >= 0 && result < min) {
                min = 1 + result;
            }
        }

        dp[amount - 1] = min == Integer.MAX_VALUE ? -1 : min;
        return dp[amount - 1];
    }
}

Last modified October 4, 2020