# LeetCode 121. Best Time to Buy and Sell Stock: C++ Solution

## Problem Statement

You are given an array for which the `ith`

element is the price of a stock on day `i`

.

If you could only complete at most one transaction (i.e, buy one and sell one share of the stock), write a function to find the maximum profit.

```
Function Signature (C++):
int maxProfit(vector<int>& prices)
Inputs:
prices = [7, 1, 5, 3, 6, 4]
Outputs:
5
We can buy at 1 and then sell at 6 => 6 - 1 = 5;
Note that the answer is not from 7 - 1, because we cannot buy at 1 and then sell at 7.
Inputs:
prices = [7, 6, 4, 3, 1]
Outputs:
0
No transaction is done - we would only lose money.
```

## TL;DR Code Solution

```
int maxProfit(vector<int>& prices) {
int currentMin = INT_MAX;
int result = 0;
for (int i = 0; i < prices.size(); i++) {
result = max(result, prices[i] - currentMin);
currentMin = min(currentMin, prices[i]);
}
return result;
}
```