Stock buy sell
Problem Statement
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.
Brute Force
Intuition
Understand the problem and develop a solution approach.
Initialize two variables: min_price and max_profit.
-> min_price = minimum price in the array. -> max_profit = 0.
Iterate through the array, and for each price:
-> Update min_price to the minimum price seen so far. -> Update max_profit to the maximum profit seen so far, or the current price minus min_price, whichever is greater.
Return max_profit.
Approach
Initialize two variables: min_price and max_profit.
-> min_price = minimum price in the array. -> max_profit = 0.
Iterate through the array, and for each price:
-> Update min_price to the minimum price seen so far. -> Update max_profit to the maximum profit seen so far, or the current price minus min_price, whichever is greater.
Return max_profit.
Code (Java)
int maxProfit(ArrayList<int> &prices)
{
int minprice = prices[0];
int ans = 0;
for (int i = 1; i < prices.size(); i++)
{
ans = max(ans, prices[i] - minprice);
minprice = min(minprice, prices[i]);
}
return ans;
}
Complexity Analysis
Time complexity: O(N) Space complexity: O(0)
Quick Revision (Brute Force)
- Initialize two variables: min_price and max_profit.
- min_price = minimum price in the array.
- max_profit = 0.
- Iterate through the array, and for each price:
- Update min_price to the minimum price seen so far.