122. Best Time to Buy and Sell Stock II

动态规划，dp[i]=max(dp[i-1],dp[k]+prices[i]-nums[k+1])，k+1>=0&&k+1<=i-1;

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

可以用贪心法；

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