动规训练三：Leetcode 322. 零钱兑换

输入：coins = [1, 2, 5], amount = 11
输出：3 
解释：11 = 5 + 5 + 1

输入：coins = [2], amount = 3
输出：-1

输入：coins = [1], amount = 0
输出：0

输入：coins = [1], amount = 1
输出：1

输入：coins = [1], amount = 2
输出：2

public class Solution {
    public int coinChange(int[] coins, int amount) {
        int max = amount + 1;
        int[] dp = new int[amount + 1];
        // 这里我们还得给dp[i]赋予一个尽量大的初始值
        for(int i = 0; i <= amount; i++) {
                dp[i] = amount + 1;
        }
        dp[0] = 0;
        for (int i = 1; i <= amount; i++) {
            // 计算机 dp[i] 所需要的最少硬币数量
            for (int j = 0; j < coins.length; j++) {
                if (coins[j] <= i) {
                    dp[i] = Math.min(dp[i], dp[i - coins[j]] + 1);
                }
            }
        }
        return dp[amount] > amount ? -1 : dp[amount];
    }
}