# Best Time to Buy and Sell Stock

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

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.

Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.

Example 1:

```
Input: prices = [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.
```

Example 2:

```
Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.
```

## Solution:

```
/**
* @param {number[]} prices
* @return {number}
*/
var maxProfit = function(prices) {
var res = 0;
var min = Infinity;
for(var i=0; i<prices.length; i++){
if(prices[i]<min){
min = prices[i];
}else{
res = Math.max(res, prices[i]-min)
}
}
return res;
};
```