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.

 

Constraints:

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

---

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

Time Limit Exceeded

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class Solution {
    public int maxProfit(int[] prices) {
        int maxProfit=0;
        int minPrice=Integer.MAX_VALUE;

        for (int i=0; i<prices.length; i++){
            if (prices[i]<minPrice){
                minPrice=prices[i];
            }else if(prices[i]-minPrice>maxProfit){
                maxProfit = prices[i]-minPrice;
            }
        }
        return maxProfit;
    }
}