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BuyAndSellStock.java
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BuyAndSellStock.java
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package Leetcode;
/**
* @author kalpak
*
* 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 <= 10^5
* 0 <= prices[i] <= 10^4
*/
public class BuyAndSellStock {
public static int maxProfit(int[] prices) {
return computeMaxProfitRecursive(prices, 0, Integer.MAX_VALUE, 0);
}
private static int computeMaxProfitRecursive(int[] prices, int currentIdx, int minStockPrice, int maxProfit) {
if(currentIdx >= prices.length)
return maxProfit;
maxProfit = Math.max(maxProfit, prices[currentIdx] - minStockPrice);
minStockPrice = Math.min(minStockPrice, prices[currentIdx]);
return computeMaxProfitRecursive(prices, currentIdx + 1, minStockPrice, maxProfit);
}
public static int maxProfitIterative(int[] prices) {
int result = Integer.MIN_VALUE;
int minStockPrice = Integer.MAX_VALUE;
for(int i = 0; i < prices.length; i++) {
result = Math.max(result, prices[i] - minStockPrice);
minStockPrice = Math.min(minStockPrice, prices[i]);
}
return result;
}
public static void main(String[] args) {
int[] prices = new int[]{7,1,5,3,6,4};
System.out.println(maxProfit(prices));
System.out.println(maxProfit(prices));
}
}