Maximize One Chronological Stock Transaction
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
Choose one day to buy one share and a later, different day to sell it. Given daily prices in chronological order, return the largest achievable profit from this single transaction. Return 0 if no profitable transaction exists; making no transaction is allowed.
```cpp
int maxProfit(vector<int>& prices);
```
### Examples
```text
Input: prices = [9,2,8,1,6]
Output: 6
```
Buying at 2 and later selling at 8 yields 6. The later price 1 cannot be paired with the earlier price 8 as a sale.
```text
Input: prices = [6,4,4,1]
Output: 0
```
### Constraints
- The number of days is between 1 and 100000.
- Every price is between 0 and 10000, inclusive.
Overview: Maximize profit from one buy-before-sell transaction using the minimum earlier price and constant extra space.