121.买卖股票的最佳时机

Python:

class Solution(object):def maxProfit(self, prices):""":type prices: List[int]:rtype: int"""if len(prices)==0:return 0dp=len(prices)*[0]minprice=int(prices[0])for i in range (1,len(prices)):minprice=min(minprice,prices[i])dp[i]=max(dp[i-1],prices[i]-minprice)return dp[-1]

java:

class Solution {public int maxProfit(int[] prices) {int n = prices.length;int []dp=new int[n];int minpri=prices[0];for (int i=1;i<n;i++){dp[i] = Math.max(dp[i-1],prices[i]-minpri);minpri=Math.min(prices[i],minpri);}return dp[n-1];}
}

121.买卖股票的最佳时机 II

Python:

class Solution:def maxProfit(self, prices: List[int]) -> int:n=len(prices)dp=[[0 for _ in range (2)] for _ in range(n)]dp[0][0]=0dp[0][1]=-prices[0]for i in range (1,n):dp[i][0]=max(dp[i-1][0],dp[i-1][1]+prices[i])dp[i][1]=max(dp[i-1][1],dp[i-1][0]-prices[i])return dp[-1][0]

Java:

class Solution {public int maxProfit(int[] prices) {int n = prices.length;int [][] dp=new int[n][2];dp[0][0]=0;dp[0][1]=-prices[0];for (int i=1; i<n;i++){dp[i][0]=Math.max(dp[i-1][0],dp[i-1][1]+prices[i]);dp[i][1]=Math.max(dp[i-1][1],dp[i-1][0]-prices[i]);}return dp[n-1][0];}
}

Python贪心算法：

class Solution:def maxProfit(self, prices: List[int]) -> int:res=0for i in range(1,len(prices)):if prices[i]>prices[i-1]:res+=(prices[i]-prices[i-1])else:continuereturn res