[LeetCode 121] Best Time to Buy and Sell Stock

문제 바로가기

Description

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You are given an array prices where prices[i] is the price of a given stock on the i^th 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

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• 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

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

Constraints

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• 1 <= prices.length <= 10^5
• 0 <= prices[i] <= 10^4

Code

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내 제출

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class Solution {
    public int maxProfit(int[] prices) {
        int ans = 0, mi = prices[0];
        for (int v : prices) {
            ans = Math.max(ans, v - mi);
            mi = Math.min(mi, v);
        }
        return ans;
    }
}

Runtime	Memory
1 ms	61.5 MB

다른 풀이

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

Reference

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• https://github.com/doocs/leetcode/blob/main/solution/0100-0199/0121.Best%20Time%20to%20Buy%20and%20Sell%20Stock/Solution.java