# 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:

```python
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:

```python
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:

```python
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

```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](https://github.com/ChunhThanhDe/Leetcode-Top-Interview/blob/main/Topic%201%20Array%20-%20String/008%20Best%20Time%20to%20Buy%20and%20Sell%20Stock%20II/Solution.java).