Buy and Sell Stocks

Problem Statement

You are given an array prices[] where prices[i] represents the price of a stock on the i-th day. You need to find the maximum profit you can achieve by buying and selling the stock at most once. If no profit can be made, return 0.

Example

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.

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Approach

1. Initialize Variables:

   • Maintain min_price to track the lowest price seen so far.

   • Maintain max_profit to store the maximum possible profit.

2. Iterate Through Prices:

   • If the current price is lower than min_price, update min_price.

   • Calculate the profit by subtracting min_price from the current price.

   • Update max_profit if the calculated profit is greater than max_profit.

3. Return max_profit after traversing the array.

Code implementation:

int maxProfit(vector<int>& prices) {

int i,minEle=prices[0],cost,profit=0;

for(i=0;i<prices.size();i++){

cost=(prices[i]-minEle);

profit=max(profit,cost);

minEle=min(prices[i],minEle);
     }

return profit;

}

Time and Space Complexity

• Time Complexity: O(n), since we traverse the array once.

• Space Complexity: O(1), as we use only two extra variables.

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Edge Cases Considered

• When prices are decreasing, e.g., [7,6,4,3,1], output should be 0.

• When prices have only one element, output should be 0.

• When prices array is empty, output should be 0.

problem link:https://leetcode.com/problems/best-time-to-buy-and-sell-stock/