1+ package com .leetcode .arrays ;
2+ 3+ /**
4+ * Problem: https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
5+ *
6+ * @author rampatra
7+ * @since 2019年04月23日
8+ */
9+ public class BuySellStocks {
10+ 11+ /**
12+ * Time complexity: O(n)
13+ * where,
14+ * n = no. of stock prices
15+ * <p>
16+ * Runtime: <a href="https://leetcode.com/submissions/detail/224463627/">0 ms</a>.
17+ *
18+ * @param prices
19+ * @return
20+ */
21+ public static int maxProfit (int [] prices ) {
22+ int profit = 0 ;
23+ int buyPrice = Integer .MAX_VALUE ;
24+ 25+ for (int i = 0 ; i < prices .length ; i ++) {
26+ if (prices [i ] < buyPrice ) {
27+ buyPrice = prices [i ];
28+ } else if (prices [i ] - buyPrice > profit ) {
29+ profit = prices [i ] - buyPrice ;
30+ }
31+ }
32+ 33+ return profit ;
34+ }
35+ 36+ public static void main (String [] args ) {
37+ 38+ System .out .println (maxProfit (new int []{7 , 1 , 5 , 3 , 6 , 4 }));
39+ System .out .println (maxProfit (new int []{7 , 1 , 5 , 0 , 6 , 4 }));
40+ System .out .println (maxProfit (new int []{4 , 3 , 2 , 1 }));
41+ 42+ // edge cases
43+ System .out .println (maxProfit (new int []{}));
44+ System .out .println (maxProfit (new int []{1 }));
45+ }
46+ }
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