Buy and Sell Stock Once

Buy and Sell Stock Once

Problem Statement

Write a program that takes an array of stock prices and return maximum profit that can be made by buying and selling one stock. 

Problem Solving

• This question I have seen a hundred times, lets kill this once and for all. 
• So a list of array with number and we are interested in the max profit. 
• Max profit would be obtained by buying at a local minima followed by a local maxima. 
• The brute force way would be for each day consider buying and then calculate how much profit we get by selling on remaining following days.
• This would surely give correct ans with quadratic time complexity.  
• A linear approach would be to iterate through the array in ascending time and keep registering max_profit.
• At every element we check whether the element is a local minima if so the is it less than the current local minima, if yes then we update out buying option.
• Otherwise we continue iterating and registering max_profit. 
• Stop when we reach the last element.  
• Find code here.  

Learning

• Like the previous problem problem solving really is emotionally challenging despite being able to solve the problem in decent time. The emotional strength to face it is enormous. 
• Thinking the brute force way was obviously morale boosting that at least there is a way. 
• Further optimizing it was easy and confidence boosting. 
• I think I should now face problems with more confidence and these are really not that difficult. 
• One more thing, today this problem was solved without any compiler errors and in one go.