[121]Best Time to Buy and Sell Stock

【题目描述】

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.

【思路】

动态规划的题目。

状态转移方程是：

s(n+1)=0,若prices(n+1)<prices(n)

s(n+1)=s(n)+prices(n+1)-prices(n),若prices(n+1)>prices(n)

再求最大的s

【代码】

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