Best Time to Buy and Sell Stock in Java

The challenge

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

Example 1:

Input: [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.
             Not 7-1 = 6, as selling price needs to be larger than buying price.

Example 2:

Input: [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.

The solution in Java

class Solution { public int maxProfit(int[] prices) { // create a profit variable to return int maxprofit = 0; // loop through the original array for (int i=0; i<prices.length-1; i++) { // loop through the array from the next item on for (int j=i+1; j<prices.length; j++) { // if in bounds and next is greater than current if (j<prices.length && prices[j]>prices[i]) { // work out profit int tmp = prices[j]-prices[i]; // report the profit if (tmp>maxprofit) maxprofit = tmp; } } } // return out profit return maxprofit; } }
Code language: Java (java)
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