Merge pull request keon#75 from dong-jy/patch-2

Update buy_sell_stock.py

Author: ankit167

dp/buy_sell_stock.py

@@ -20,10 +20,24 @@
 """
 
 
-def max_profit(prices):
+# O(n^2) time
+def max_profit_naive(prices):
+    """
+    :type prices: List[int]
+    :rtype: int
+    """
+    max_so_far = 0
+    for i in range(0, len(prices) - 1):
+        for j in range(i + 1, len(prices)):
+            max_so_far = max(max_so_far, prices[j] - prices[i])
+    return max_so_far
+
+
+# O(n) time
+def max_profit_optimized(prices):
     """
     input: [7, 1, 5, 3, 6, 4]
-    diff : [X,-6, 5,-2, 3,-2]
+    diff : [X, -6, 4, -2, 3, -2]
     :type prices: List[int]
     :rtype: int
     """