518. Coin Change 2

coin循环要在外面 从小到大 不会有重复

 

class Solution {
    public int change(int amount, int[] coins) {
        // if(coins.length == 0) return 1;
        int[] dp = new int[amount + 1];
        dp[0] = 1;
        Arrays.sort(coins);
        for(int j = 0; j < coins.length; j++){
            for(int i = 1; i <= amount; i++){
                if(coins[j] <= i){
                    dp[i] += dp[i - coins[j]];
                }
            }
        }
        return dp[amount];
        
    }
}