Leetcode_practice/5_Easy.cpp at main · uwi001-1/Leetcode_practice · GitHub

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#include<iostream>
using namespace std;

// 121. Best Time to Buy and Sell Stock

/***************
You are given an array prices where prices[i] is the price of a given stock on the ith day.
You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Example 1:
Input: prices = [7,1,5,3,6,4]
Output: 5
    Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
    Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.

Example 2:
Input: prices = [7,6,4,3,1]
Output: 0
    Explanation: In this case, no transactions are done and the max profit = 0.
***************/

class Solution {
public:
    int maxProfit(vector<int>& prices)
    {
        int least = prices[0];
        int maxProfit = 0;

        for(int i = 1; i < prices.size(); i++)
        {
            if(prices[i] < least)
            {
                least = prices[i];    // the least price in position
            }
        else
        {
            int profit = prices[i] - least;
            if(profit > maxProfit)   //get the highest profit
            {
                maxProfit = profit;
            }
        }
    }
    return maxProfit;
    }
};

/*****
class Solution {
public:
    int maxProfit(vector<int>& prices)
    {
        int least = prices[0];
        int L_index = 0;

        //find the least price day
        for(int i = 1; i < prices.size(); i++)
        {
            if(prices[i] < least)
            {
                if(i != prices.size() - 1)
                {
                    least = prices[i];
                    L_index = i;
                }
            }
        }
        if(L_index == prices.size() - 1)
            return 0;

        int high = prices[L_index];
        //loop for the high price day after buying
        for(int j = L_index + 1; j < prices.size(); j++)
        {
            if(prices[j] > high)
            {
                high = prices[j];
            }
        }

        int profit = high - least;
        if(profit > 0)
            return profit;
        else
            return 0;
    }
};
*****/