# 问题描述

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.

Example 1:

`Input: [7, 1, 5, 3, 6, 4]Output: 5​max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger than buying price)`

Example 2:

`Input: [7, 6, 4, 3, 1]Output: 0​In this case, no transaction is done, i.e. max profit = 0.`

# Python

DP的入门题目,先用模拟做

`class Solution(object):    def maxProfit(self, prices):        """        :type prices: List[int]        :rtype: int        """        import sys        lowprice = sys.maxint        profit = 0        for price in prices:            if price < lowprice:                lowprice = price            if price - lowprice > profit:                profit = price -lowprice        return profit`

# Java

`class Solution {    public int maxProfit(int[] prices) {        int max = 0;        int curMin = Integer.MAX_VALUE;        for (int i = 0; i < prices.length; i++) {            curMin = Math.min(curMin, prices[i]);            max = Math.max(max, prices[i] - curMin);        }        return max;    }}`

# Golang

DP 求解

`package main​import (    "fmt")​func MaxProfit(prices []int) int {    low := prices    result := 0    for i := 1; i < len(prices); i++ {        if prices[i] < low {            low = prices[i]        }        if prices[i]-low > result {            result = prices[i] - low        }    }    return result}​func main() {    a := []int{7, 3, 1, 2, 6, 8}    fmt.Println(MaxProfit(a[:]))}`