(LeetCode) 121. Best Time to Buy and Sell Stock

121. Best Time to Buy and Sell Stock

• Explore : Interview > Top Interveiw Questions > Easy Collection
• 분류 : Dynamic Programming
• 난이도 : Easy

Problem

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

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.

Constraints

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

Solution

Exapnder

class Solution {
    fun maxProfit(prices: IntArray): Int {
        var min = Integer.MAX_VALUE
        var result = 0
        prices.forEachIndexed { index, i ->
            if (prices[index] < min) {
                min = prices[index]
            } else {
                if (prices[index] - min > result) {
                    result = prices[index] - min
                }
            }
        }
        return result
    }
}

Point of Thinking

• 순회하면서 가장 작은 price을 찾는다.
• 가장 작은 price와 현재 가지고 있는 최대이익과 비교하여 갱신한다.
• 배열을 한 번 다 순회하면 Accepted.