Prob:184 best time to buy and sell stock

Author: mandliya

README.md

@@ -6,7 +6,7 @@
 
 | Current Status|     Stats     |
 | :------------: | :----------: |
-| Total Problems | 183 |
+| Total Problems | 184 |
 
 </center>
 
@@ -264,3 +264,7 @@ pattern = "abba", str = "dog cat cat dog" should return true.
 pattern = "abba", str = "dog cat cat fish" should return false.
 pattern = "aaaa", str = "dog cat cat dog" should return false.
 pattern = "abba", str = "dog dog dog dog" should return false.| [word_pattern.cpp](leet_code_problems/word_pattern.cpp)|
+|You are provided a vector of numbers, where each number represents
+price of a stock on ith day. If you are permitted to only complete 
+one transaction per day (i.e buy one and sell one stock), design
+an algorithm to find the maximum profit.| [best_time_to_buy_sell.cpp](leet_code_problems/best_time_to_buy_sell.cpp)|

leet_code_problems/best_time_to_buy_sell.cpp

@@ -0,0 +1,54 @@
+/*
+ * You are provided a vector of numbers, where each number represents
+ * price of a stock on ith day. If you are permitted to only complete
+ * one transaction per day (i.e buy one and sell one stock), design
+ * an algorithm to find the maximum profit.
+ * 
+ * Input: [7, 1, 5, 3, 6, 4]
+ * Output: 5 
+ * max. difference = 6-1 = 5
+ * (not 7-1 = 6, as selling price needs to be larger than buying price)
+ * 
+ * Approach:
+ * 
+ * We need to find the maximum difference between two numbers in the array
+ * (which would be maximum profit) such that selling price(second number)
+ *  is bigger than buying price.
+ */
+
+#include <iostream>
+#include <vector>
+#include <limits>
+
+int maximum_profit(const std::vector<int>& prices)
+{
+    int min_price = std::numeric_limits<int>::max();
+    int max_profit = 0;
+    for (int i = 0; i < prices.size(); ++i) {
+        if (prices[i] < min_price) {
+            min_price = prices[i];
+        } else if (prices[i] - min_price > max_profit) {
+            max_profit = prices[i] - min_price;
+        }
+    }
+    return max_profit;
+}
+
+void print_vector(const std::vector<int>& vec) {
+    for (auto v : vec) {
+        std::cout << v << " ";
+    }
+    std::cout << std::endl;
+}
+
+int main()
+{
+    std::vector<int> prices{7, 1, 5, 3, 6, 4};
+    std::cout << "Prices of stocks in last " << prices.size()
+        << " days:" << std::endl;
+    print_vector(prices);
+    std::cout << "Maximum profit: " << maximum_profit(prices)
+        << std::endl;
+
+    return 0;
+}