122. Best Time to Buy and Sell Stock II 📈💰

Difficulty: Medium - Tags: Array, Greedy, Dynamic Programming

Description

You are given an integer array prices where prices[i] is the price of a given stock on the ith day.

On each day, you may decide to buy and/or sell the stock. You can only hold at most one share of the stock at any time. However, you can buy it and then immediately sell it on the same day.

Find and return the maximum profit you can achieve.

Examples

Example 1:

Input:

prices = [7,1,5,3,6,4]

Output:

7

Explanation:

• Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.

• Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.

• Total profit is 4 + 3 = 7.

Example 2:

Input:

prices = [1,2,3,4,5]

Output:

4

Explanation:

• Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.

• Total profit is 4.

Example 3:

Input:

prices = [7,6,4,3,1]

Output:

0

Explanation: There is no way to make a positive profit, so we never buy the stock to achieve the maximum profit of 0.

---

Solution 💡

The time complexity is $O(n)$, and the space complexity is $O(1)$, where $n$ is the number of days.

Java

class Solution {
    public int maxProfit(int[] prices) {
        int profit = 0;
        for (int i = 1; i < prices.length; i++) {
            if (prices[i] > prices[i - 1]) {
                profit += prices[i] - prices[i - 1];
            }
        }
        return profit;
    }
}

You can find the full Solution.java file here.