[Array] Add a solution to Best Time Buy Sell Stock II

Author: Yi Gu

Array/BestTimeBuySellStockII.swift

@@ -0,0 +1,24 @@
+/**
+ * Question Link: https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/
+ * Primary idea: Add all substractions if sell stock could earn money
+ * Time Complexity: O(n), Space Complexity: O(1)
+ *
+ */
+
+ class BestTimeBuySellStockII {
+    func maxProfit(_ prices: [Int]) -> Int {
+        var max = 0
+        
+        guard prices.count > 1 else {
+            return max
+        }
+        
+        for i in 1 ..< prices.count {
+            if prices[i] > prices[i - 1] {
+                max += prices[i] - prices[i - 1]
+            }
+        }
+        
+        return max
+    }
+}