zoukankan      html  css  js  c++  java
  • 【leetcode】Best Time to Buy and Sell Stock

    Question :    

    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.

    for example: array[]  = { 2, 5, 3, 8, 9, 4 } , maxProfit = 9 - 2 = 7.

    Anwser 1 :       

    class Solution {
    public:
        int maxProfit(vector<int> &prices) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
            if(prices.size() == 0) return 0;
            
            int ret = 0;
            
            int len = prices.size();
            int maxPrice = prices[len-1];
            for(int i = len - 1; i >= 0; i--){
                maxPrice = max(prices[i], maxPrice);    // maxPrice
                ret = max(ret, maxPrice - prices[i]);   // maxProfit
            }
            
            return ret;
        }
    };

    注意点:

    最大利润,应该是先买的最低价与后卖的最高价的差值,因此需要考虑时间先后顺序

    Anwser 2 :       

    class Solution {
    public:
        int maxProfit(vector<int> &prices) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
            int maxp = 0;
            int dp = 0;        
            for(int i = prices.size()-2; i >= 0 ;i--)
            {
                if(dp >= 0){
                    dp += (prices[i+1] - prices[i]);
                } else {
                    dp = max(0, prices[i+1] - prices[i]);
                }
                maxp = max(dp, maxp);
            }  
            return maxp;
        }
    };

    说明:

    1) 此法把两数之间最大差,转化为了求两数组之间最大和

    2) dp += (prices[i+1] - prices[i]) 实际上是 dp +=  (prices[i+1] - prices[i])  +  (prices[i] - prices[i-1])  +  (prices[i-1] - prices[i-2]) + ... =  (prices[i] - prices[j])   (i > j)

    参考推荐:

    数组中数对差最大

  • 相关阅读:
    Bind和Eval的区别详解(ZT)
    .net中IndexOf和LastIndexOf的区别 
    个人学习代码保存:例3. GridView相关练习操作
    Convert.ToInt32和int.Parse有什么区别?
    个人学习代码保存:例1.asp.net DataList相关操作
    Sum(构造,枚举)
    1278 相离的圆(51nod)
    Wheels(bfs遍历,CERC 2014)
    详解 Android 的 Activity 组件
    Android应用程序变量
  • 原文地址:https://www.cnblogs.com/javawebsoa/p/3034483.html
Copyright © 2011-2022 走看看