Given an array of time and selling price find the best buying and selling time to maximize the profit

Question

Given [ (02:00, 7.5), (03:30, 7.9), (04:00, 8.0), (05:30, 6.8), (10:00, 9.01)] times and selling price we need to find the best time for buying and selling to maximize the profit. // times are in increasing order // Sample Output: Buy at 05:30 and sell at 10:00 for a profit of 2.21

I have written the logic to find the max profit but I also need to find the best buying and selling time, so I am bit stuck there

double profit(double prices[])
  {
     double maxprofit=0;

    for(int i=0;i<price.length;i++)
    {
    double min= values[i];
    for(int j=i+1;j<price.length;j++)
    {
      if(price[j]<price[min])
      min=values[min];

    }
    profit=values[i]-min;
    if(maxprofit<profit)
    maxprofit=profit;
else
continue;
}

Answer 1

There is no need to use a nested loop, there is a linear time algorithm that can solve this problem.

There is a very detailed explanation of the algorithm here.

Here is how you could fix your code:

public double maxProfit(double[] prices) {

    if (prices.length <= 1) return 0;

    double minPrice = prices[0];
    double maxSoFar = Integer.MIN_VALUE;
    double profitSoFar = Integer.MIN_VALUE;

    for (int i = 1; i < prices.length; i++){
        profitSoFar = prices[i] - minPrice;
        minPrice = Math.min(minPrice, prices[i]);
        maxSoFar = Math.max(profitSoFar, maxSoFar);

    }

    return Math.max(maxSoFar, 0);
}