Coin_Change_2.cpp

class Solution {
public:
    int change(int amount, vector<int>& coins) {
        int n = (int)coins.size();
        vector<int> dp(amount + 1, 0);
        dp[0] = 1;
        for(int i = 0; i < n; i++) {
            // for(int j = amount; j >= coins[i]; j--) {
            for(int j = coins[i]; j <= amount; j++) {
                dp[j] += dp[j - coins[i]];
            }
        }
        return dp[amount];
    }
};