LeetCode - Coin Change

문제 설명

You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money.

Return 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.

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

입출력 예시

Example 1:

Input: coins = [1,2,5], amount = 11
Output: 3
Explanation: 11 = 5 + 5 + 1

Example 2:

Input: coins = [2], amount = 3
Output: -1

Example 3:

Input: coins = [1], amount = 0
Output: 0

제약사항

1 <= coins.length <= 12
1 <= coins[i] <= 231 - 1
0 <= amount <= 104

Solution

[전략]

• DP 접근법을 이용
• bottom-up 방식으로 amount까지의 각 숫자를 만들기 위한 최소 코인의 갯수를 구함

import java.util.*;

class Solution {
    public int coinChange(int[] coins, int amount) {

        int[] countForVal = new int[amount + 1];

        Arrays.sort(coins);

        for (int i = 1; i < countForVal.length; i++) {
            calculateCount(i, countForVal, coins);
        }
        return countForVal[amount];
    }

    public void calculateCount(int subAmount, int[] countForVal, int[] coins) {

        int coinCount = -1;
        for (int i = 0; i < coins.length; i++) {
            int remainVal = subAmount - coins[i];
            if (remainVal < 0) {
                continue;
            } else if (remainVal == 0) {
                countForVal[subAmount] = 1;
                return;
            } else {
                if (countForVal[remainVal] > 0 && (coinCount == -1 || coinCount > countForVal[remainVal])) {
                    coinCount = countForVal[remainVal];
                }
            }
        }
        countForVal[subAmount] = coinCount == -1 ? -1 : coinCount + 1;
    }
}