122. 買賣股票的最佳時機 II

笨方法，算出了所有的遞增序列，當時沒有想到貪心

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        if(prices.size() == 0)
            return 0;
        int money = 0;
        int pos = 0, pre = 0, cur = 1;
        while(cur < prices.size()){
            if(prices[pre] < prices[cur]){
                pre++;
                cur++;
            }else{
                if(pre != pos){
                    money += prices[pre] - prices[pos];
                    pos = cur;
                    pre = cur;
                    cur++;
                }else{
                    pos++;
                    pre++;
                    cur++;
                }

            }
        }
        if(pos != prices.size() - 1){
            money += prices[prices.size() - 1] - prices[pos];
        }
        return money;
    }
};           

貪心

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int res = 0, n = prices.size();
        for (int i = 0; i < n - 1; ++i) {
            if (prices[i] < prices[i + 1]) {
                res += prices[i + 1] - prices[i];
            }
        }
        return res;
    }
};           

其實時間差不多，都是一遍for循環