# Problems of Best Time to Buy and Sell Stock

## 121. Best Time to Buy and Sell Stock

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete

at most one transaction(i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.Note that you cannot sell a stock before you buy one.

### Normal Solution

```
class Solution {
public int maxProfit(int[] prices) {
int n = prices.length;
if (n == 0) {
return 0;
}
int maxProfit = 0;
int minPrice = prices[0];
for (int i = 1; i < n; i++) {
maxProfit = Math.max(maxProfit, prices[i] - minPrice);
minPrice = Math.min(minPrice, prices[i]);
}
return maxProfit;
}
}
```

## 122. Best Time to Buy and Sell Stock II

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete

as many transactions as you like(i.e., buy one and sell one share of the stock multiple times).

Note:You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).

## 123. Best Time to Buy and Sell Stock III

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete

at most two transactions.

Note:You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).

## 188. Best Time to Buy and Sell Stock IV

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete

at most k transactions.

Note:You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

## 309. Best Time to Buy and Sell Stock with Cooldown

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete

as many transactions as you like(ie, buy one and sell one share of the stock multiple times) with the following restrictions:

- You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).
After you sell your stock, you cannot buy stock on next day.(ie, cooldown 1 day)

## 714. Best Time to Buy and Sell Stock with Transaction Fee

Your are given an array of integers prices, for which the ith element is the price of a given stock on day i; and a non-negative integer fee representing a transaction fee.

You may complete

as many transactions as you like, but you need to pay the transaction fee for each transaction. You may not buy more than 1 share of a stock at a time (ie. you must sell the stock share before you buy again.)Return the maximum profit you can make.