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Best Time to Buy and Sell Stock

Certification: Basic Level Accuracy: 0% Submissions: 0 Points: 5

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:

     Step 1: Buy on day 1 (price = 1)

     Step 2: Sell on day 4 (price = 6)

     Step 3: Profit = 6 - 1 = 5

     Step 4: There is no other combination that gives a higher profit
    •
Example 2
    
  
  • Input: prices = [7,6,4,3,1]
    • 
  
  • Output: 0
    • 
  
  • Explanation:

     Step 1: Prices are in decreasing order

     Step 2: No profit is possible as buying and then selling later always results in a loss

     Step 3: Return 0 as we choose not to do any transaction
    •
Constraints
    
  
  • 1 <= prices.length <= 10^5
    • 
  
  • 0 <= prices[i] <= 10^4
    • 
  
  • You can only buy once and sell once
    • 
  
  • Time Complexity: O(n) where n is the length of the prices array
    • 
  
  • Space Complexity: O(1)
    •
ArraysNumberTech MahindraGoldman Sachs
Editorial

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Hint
Solution

Solution Hints

    
  
  • Use a single pass approach to track the minimum price seen so far
    • 
  
  • For each price, calculate the potential profit by subtracting the minimum price from the current price
    • 
  
  • Update the maximum profit if the current potential profit is greater
    • 
  
  • Continue this process for all prices
    • 
  
  • Return the maximum profit found (or 0 if no profit is possible)
    •

Steps to solve by this approach:

 Step 1: Check if the array has less than 2 elements. If so, return 0 as no profit is possible.

 Step 2: Initialize minPrice to the first price and maxProfit to 0.

 Step 3: Iterate through the prices array starting from the second price.

 Step 4: For each price, check if it's lower than the minPrice. If so, update minPrice.

 Step 5: If the current price is not a new minimum, calculate the potential profit by selling at the current price.

 Step 6: Update maxProfit if the current potential profit is greater than the existing maxProfit.

 Step 7: After examining all prices, return the maxProfit.

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