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BestTimeToBuyAndSellStock.java
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BestTimeToBuyAndSellStock.java
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package algorithms;
/**
* 121. Best Time to Buy and Sell Stock
* https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
* Difficulty : Easy
* Related Topics : Array, Dynamic Programming
*
* 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
*
* created by Cenk Canarslan on 2021-01-17
*/
public class BestTimeToBuyAndSellStock {
/**
* O(n)
* Runtime: 2 ms, faster than 29.62% of Java online submissions
* Memory Usage: 52 MB, less than 5.47% of Java online submissions
*
* @param prices
* @return
*/
public int maxProfit(int[] prices) {
int maxProfit = 0;
int min = Integer.MAX_VALUE;
for (int i = 0; i < prices.length; i++) {
if (prices[i] < min) {
min = prices[i];
} else {
maxProfit = Math.max(maxProfit, prices[i] - min);
}
}
return maxProfit;
}
// /**
// * O(n)
// * Runtime: 4 ms, faster than 20.04% of Java online submissions
// * Memory Usage: 105.1 MB, less than 5.47% of Java online submissions
// *
// * @param prices
// * @return
// */
// public int maxProfit(int[] prices) {
// int lowestDay = 0;
// int maxProfit = 0;
//
// for (int i = 0; i < prices.length; i++) {
// if (prices[lowestDay] > prices[i]) {
// lowestDay = i;
// }
// if (prices[i] - prices[lowestDay] > maxProfit) {
// maxProfit = prices[i] - prices[lowestDay];
// }
// }
// return maxProfit;
// }
public static void main(String[] args) {
BestTimeToBuyAndSellStock bestTime = new BestTimeToBuyAndSellStock();
System.out.println(bestTime.maxProfit(new int[]{7, 1, 5, 3, 6, 4})); // 5
System.out.println(bestTime.maxProfit(new int[]{7, 6, 4, 3, 1})); // 0
}
}