Best Time to Buy and Sell Stock

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

这道题是典型的局部最优和全局最优问题，son不断地更新，parent取parent和son的最大值