diff --git a/src/main/kotlin/Main.kt b/src/main/kotlin/Main.kt
index 1e277c1..3d46f90 100644
--- a/src/main/kotlin/Main.kt
+++ b/src/main/kotlin/Main.kt
@@ -1,5 +1,7 @@
 package main.kotlin
 
+import main.kotlin.dsalgoleetcode.BuyAndSellStock
+import main.kotlin.dsalgoleetcode.ContainsDuplicate
 import main.kotlin.dsalgoleetcode.LinkedListCycleDetection
 import main.kotlin.dsalgoleetcode.ListNode
 import main.kotlin.dsalgoleetcode.LongestSubstring
@@ -30,4 +32,16 @@ fun main() {
     node3.next = node1 // cycle back to x
     val llcdResult = linkedListCycleDetection.hasCycle(node1)
     println("Has cycle $llcdResult")
+
+    // Calling Contains Duplicate
+    val containsDuplicate = ContainsDuplicate()
+    val containsDuplicateResult = containsDuplicate
+        .containsDuplicate(intArrayOf(1,2,3,1,0,1))
+    println("Contains Duplicate Integers $containsDuplicateResult")
+
+    // Calling Buy and Sell Stock
+    val buyAndSellStock = BuyAndSellStock()
+    val bnsResult = buyAndSellStock.maxProfit(intArrayOf(1,4,8,0,2))
+    println("Max profit : $bnsResult")
+
 }
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diff --git a/src/main/kotlin/dsalgoleetcode/BuyAndSellStock.kt b/src/main/kotlin/dsalgoleetcode/BuyAndSellStock.kt
new file mode 100644
index 0000000..385576b
--- /dev/null
+++ b/src/main/kotlin/dsalgoleetcode/BuyAndSellStock.kt
@@ -0,0 +1,33 @@
+package main.kotlin.dsalgoleetcode
+
+/**
+ * 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.
+ * */
+
+class BuyAndSellStock {
+
+    fun maxProfit(prices: IntArray): Int {
+
+        var minPrice = Int.MAX_VALUE
+        var maxProfit = 0
+
+        for (price in prices){
+            if( price < minPrice){
+                minPrice = price
+            } else{
+                maxProfit = maxOf(maxProfit, price - minPrice)
+            }
+        }
+        return maxProfit
+    }
+}
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diff --git a/src/main/kotlin/dsalgoleetcode/ContainsDuplicate.kt.kt b/src/main/kotlin/dsalgoleetcode/ContainsDuplicate.kt.kt
new file mode 100644
index 0000000..4e35c07
--- /dev/null
+++ b/src/main/kotlin/dsalgoleetcode/ContainsDuplicate.kt.kt
@@ -0,0 +1,27 @@
+package main.kotlin.dsalgoleetcode
+
+/**
+ * Contains Duplicate
+ * Given an integer array nums, return true if any value appears at least twice in the
+ * array, and return false if every element is distinct.
+ *
+ * Example 1:
+ * Input: nums = [1,2,3,1]
+ * Output: true
+ * Explanation:
+ * The element 1 occurs at the indices 0 and 3.
+ * */
+
+class ContainsDuplicate {
+
+    fun containsDuplicate(nums: IntArray): Boolean {
+
+        val seen = mutableSetOf<Int>()
+        for(i in nums){
+            if( i in seen)
+                return true
+            seen.add(i)
+        }
+        return false
+    }
+}
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