CareerCup

public int maxProfit(int[] arr){
	int maxP = 0;
	int minElement = arr[0];
	if(arr.length==0)
		return maxP;
	for(int i=1;i<arr.length;i++){
		if(arr[i]>minElement){
			if(maxP <(arr[i]-minElement))
				maxP = arr[i]-minElement;
		}else{
			minElement = arr[i];
		}
	}
	return maxP;
}

in Scala:

object MaxProfitSingleBuy {
  
  def main(args: Array[String]): Unit = {   
    val a = Array(100, 120, 150, 180, 200, 40, 56, 90, 280)    
    println(getMaxProfitSingleBuy(a))
  }   
    
  def getMaxProfitSingleBuy(a:Array[Int]) : Int = {        
    var i = 0  
    var j = 0
    var max = -1
    var maxI = -1
    var maxJ = -1
    
    while (i < a.length - 1) {            
      while (i < a.length-1 && a(i) > a(i + 1)) i += 1
      
      j = i + 1
      while (j < a.length-1 && a(j) < a(j + 1)) j += 1
      
      // found local maxima
      if (a(j) - a(i) > max) {            
        max = a(j) - a(i)
        maxI = i
        maxJ = j
      }
      
      i += 1
    }
    return max
  }
  
}

in Javascript:

function getMaxProfit(stockPrices) {
    // sort array ascending numerically
    stockPrices.sort((x, y) => { return (x - y); });
    return (stock_prices[stock_prices.length - 1] - stock_prices[0]);
}

double maxProfit(std::vector<double> & prices)
{
    double minSoFar = std::numeric_limits<double>::max();
    double maxProfit = 0;
    for( auto const& price: prices)
    {
        double CurrentMaxProfit = price - minSoFar;
        maxProfit = std::max(CurrentMaxProfit, maxProfit);
        minSoFar= std::min(price, minSoFar);        
    }    
    return maxProfit;
}

Do indices in the stock array indicate time? Like every stock price at every minute? or are we trying to just get the max profit of the given values?

int MaxProfit(vector<int> const &prices)
{
    int max_profit = 0;
    int buy_price = numeric_limits<int>::max();
    for (int price : prices) {
        if (price < buy_price) {
            buy_price = price;
        } else {
            max_profit = max(max_profit, price - buy_price);
        }
    }
    return max_profit;
}