leetcode@ [121]Best Time to Buy and Sell Stock

 1 class Solution {
 2 public:
 3     int maxProfit(vector<int>& prices) {
 4         if(prices.size()<=1) return 0;
 5         
 6         int dp[prices.size()];
 7         for(int i=0;i<prices.size();++i) dp[i]=0;
 8         
 9         dp[0]=prices[0];
10         for(int i=1;i<prices.size();++i){
11             dp[i]=min(dp[i-1],prices[i]);
12         }
13         
14         int ans=-1;
15         for(int i=0;i<prices.size();++i){
16             ans=max(ans,prices[i]-dp[i]);
17         }
18         return ans;
19     }
20 };