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Best Time to Buy and Sell Stock

Certification: Basic Level Accuracy: 100% Submissions: 2 Points: 5

Write a Java program to find the maximum profit by buying and selling a 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.
      • 

    • No other transaction would result in a higher profit.
      • 

    • Therefore, the maximum profit is 5.
      • 

    •
Example 2
    

  • Input: prices = [7,6,4,3,1]
    • 

  • Output: 0
    • 

  • Explanation:

      

    • The price keeps decreasing every day, so no transaction would result in a profit.
      • 

    • The best we can do is not to conduct any transaction, which gives a profit of 0.
      • 

    • Therefore, the maximum profit is 0.
      • 

    •
Constraints
    

  • 1 ≤ prices.length ≤ 10^5
    • 

  • 0 ≤ prices[i] ≤ 10^4
    • 

  • Time Complexity: O(n)
    • 

  • Space Complexity: O(1)
    •
NumberEYSamsung
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Hint
Solution

Solution Hints

    
  
  • Use a single pass approach to find the maximum profit
    • 
  
  • Keep track of the minimum price seen so far
    • 
  
  • For each price, calculate the potential profit if you sell at that price
    • 
  
  • Update the maximum profit if a larger profit is found
    • 
  
  • Return the maximum profit at the end
    •

Steps to solve by this approach:

 Step 1: Check if the input array is valid (not null and has at least 2 elements). If not, return 0.

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

 Step 3: Iterate through the prices starting from the second day.

 Step 4: If the current price is less than minPrice, update minPrice.

 Step 5: If selling at the current price yields a higher profit, update maxProfit.

 Step 6: Return the maximum profit after processing all prices.

 Step 7: Output: 5 for example 1 and 0 for example 2.

Submitted Code :