leetcode - 121. Best Time to Buy and Sell Stock

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

문제 : 가격이 price[i]로 주어진다. 특정 가격으로 사서, 미래에 팔려고 하는데 언제 팔아야 가장 높은 수익을 올릴수

있을까?

 

풀이

class Solution {
    public int maxProfit(int[] prices) {
        
        int l = 0;//최소값을 저장할 포인터
        int sum = 0;//최대 이익 profit 값
        for(int i=1;i<prices.length;i++){
            if(prices[l] >= prices[i]) l = i;//최소값을 갱신해준다.
            else sum = Math.max(sum, prices[i] - prices[l]);
        }
        if(l==prices.length) return 0;//특정날에 사도 최대이득을 볼수없을때
        
        return sum;
    }
}