Problem of The Day: Best Time to Buy and Sell Stock

2 min read 521 words

Problem Statement

leetcode problem link

Solution [TLE]

public class Solution {
    public int MaxProfit(int[] prices) {
        int result = 0;
        for (int i = 0; i < prices.Length - 1; i++) {
            for (int j = i + 1; j < prices.Length; j++) {
                result = Math.Max(result, prices[j] - prices[i]);
            }
        }
        return result;
    }
}

Solution [Accepted]

public class Solution {
    public int MaxProfit(int[] prices) {
        int result = 0;
        int minPrice = int.MaxValue;
        int maxPrice = int.MinValue;
        foreach(int price in prices) {
           minPrice = Math.Min(price, minPrice);
           result = Math.Max(result, price - minPrice);
        }
        return result;
    }
}

Time: O(n) Space: O(1)

Editorial

Approach 2: One Pass

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        min_price = float("inf")
        max_profit = 0
        for i in range(len(prices)):
            if prices[i] < min_price:
                min_price = prices[i]
            elif prices[i] - min_price > max_profit:
                max_profit = prices[i] - min_price

        return max_profit

public class Solution {
    public int MaxProfit(int[] prices) {
        int minprice = int.MaxValue;
        int maxprofit = 0;
        for (int i = 0; i < prices.Length; i++) {
            if (prices[i] < minprice)
                minprice = prices[i];
            else if (prices[i] - minprice > maxprofit)
                maxprofit = prices[i] - minprice;
        }

        return maxprofit;
    }
}