src/main/java/com/fishercoder/solutions/_322.java

package com.fishercoder.solutions;

public class _322 {

    public static class Solution1 {
        /**
         * credit: https://leetcode.com/problems/coin-change-2/discuss/99212/Knapsack-problem-Java-solution-with-thinking-process-O(nm)-Time-and-O(m)-Space
         */
        public int coinChange(int[] coins, int amount) {
            if (amount < 1) {
                return 0;
            }
            return coinChange(coins, amount, new int[amount]);
        }

        private int coinChange(int[] coins, int rem, int[] count) {
            if (rem < 0) {
                return -1;
            }
            if (rem == 0) {
                return 0;
            }
            if (count[rem - 1] != 0) {
                return count[rem - 1];
            }
            int min = Integer.MAX_VALUE;
            for (int coin : coins) {
                int res = coinChange(coins, rem - coin, count);
                if (res >= 0 && res < min) {
                    min = 1 + res;
                }
            }
            count[rem - 1] = (min == Integer.MAX_VALUE) ? -1 : min;
            return count[rem - 1];
        }
    }

}