LeetCode link: 122. Best Time to Buy and Sell Stock II
You are given an integer array prices where prices[i] is the price of a given stock on the i-th 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 then immediately sell it on the same day.
Find and return the maximum profit you can achieve.
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[Example 1]
Input: 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.
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[Example 2]
Input: 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.
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[Example 3]
Input: 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.
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[Constraints]
1 <= prices.length <= 3 * 10000
0 <= prices[i] <= 10000
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This problem can be solved using Dynamic programming.
Detailed solutions will be given later, and now only the best practices in 3 to 7 languages are given.
- Time:
O(n). - Space:
O(n).
class Solution:
def maxProfit(self, prices: List[int]) -> int:
# states:
# 0: hold stock
# 1) keep holding
# 2) today just bought
# 1: no stock
# 1) keep no stock
# 2) today just sold
dp = [-prices[0], 0]
for price in prices[1:]:
dc = dp.copy()
dp[0] = max(dc[0], dc[1] - price)
dp[1] = max(dc[1], dc[0] + price)
return dp[1]class Solution:
# 0: have stock
# 1) just bought
# 2) keep holding
# 1: have no stock
# 1) just sold
# 2) keep no stock
def maxProfit(self, prices: List[int]) -> int:
dp = [-prices[0], 0]
for price in prices[1:]:
dc = dp.copy()
dp[0] = -price
dp[1] = max(dc[1], dc[1] + dc[0] + price)
return dp[-1]// Welcome to create a PR to complete the code of this language, thanks!// Welcome to create a PR to complete the code of this language, thanks!// Welcome to create a PR to complete the code of this language, thanks!var maxProfit = function (prices) {
const dp = [-prices[0], 0]
for (let i = 1; i < prices.length; i++) {
const dc = [...dp]
dp[0] = Math.max(dc[0], dc[1] - prices[i])
dp[1] = Math.max(dc[1], dc[0] + prices[i])
}
return dp[1]
};func maxProfit(prices []int) int {
dp := []int{-prices[0], 0}
for i := 1; i < len(prices); i++ {
dc := slices.Clone(dp)
dp[0] = max(dc[0], dc[1] - prices[i])
dp[1] = max(dc[1], dc[0] + prices[i])
}
return dp[1]
}# Welcome to create a PR to complete the code of this language, thanks!// Welcome to create a PR to complete the code of this language, thanks!// Welcome to create a PR to complete the code of this language, thanks!