class Solution {
public:
    int maxProfit(vector<int>& prices) {
        if (prices.empty() || prices.size() <= 1) return 0;

        int ans = 0;
        for (int i = 1; i < prices.size(); ++i) {
            if (prices[i] > prices[i-1]) {  // 賣出有利可圖
                ans += (prices[i] - prices[i-1]);
            }
        }

        return ans;
    }
};