BestTimeToBuyAndSellStock121.kt

package easy

/**
 * 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
 */
fun maxProfit(prices: IntArray): Int {
    var sellingPrice =0
    var maxProfit = 0

    for(i in prices.size-1 downTo 0)
    {
        sellingPrice = Math.max(sellingPrice,prices[i])

        maxProfit = Math.max(maxProfit,sellingPrice-prices[i])
    }

    return maxProfit
}