122.Best Time to Buy and Sell Stock II

tags: `Medium`,`Array`,`DP`,`Greedy`

題目描述

You are given an 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.

範例

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.

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.

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.

Constraints:

1 <= prices.length <= 10⁵
0 <= prices[i] <= 10⁴

解答

Javascript














function maxProfit(prices) {
  let max = 0;
  let minPrice = prices[0];
  for (let i = 1; i < prices.length; i++) {
    if (prices[i] < minPrice) {
      minPrice = prices[i];
    } else if (prices[i] > minPrice) {
      max += prices[i] - minPrice;
      minPrice = prices[i];
    }
  }

  return max;
}

Marsgoat Dec 23, 2022

Python







class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        pre, ans = math.inf, 0
        for price in prices:
            ans += max(0, price - pre)
            pre = price
        return ans

Yen-Chi ChenFri, Dec 23, 2022

Reference

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