diff --git a/1-two-sum/1-two-sum.cs b/1-two-sum/1-two-sum.cs
new file mode 100644
index 0000000..f10906e
--- /dev/null
+++ b/1-two-sum/1-two-sum.cs
@@ -0,0 +1,14 @@
+public class Solution {
+    public int[] TwoSum(int[] nums, int target) {
+    Dictionary<int, int> map = new Dictionary<int, int>();
+    for (int i = 0; i < nums.Length; i++) {
+        int complement = target - nums[i];
+        if (map.ContainsKey(complement)) {
+            return new int[] { map[complement], i };
+        }
+        map[nums[i]] = i;
+    }
+    throw new Exception("No two sum solution");
+}
+
+}
\ No newline at end of file
diff --git a/1-two-sum/1-two-sum.js b/1-two-sum/1-two-sum.js
new file mode 100644
index 0000000..c8eba31
--- /dev/null
+++ b/1-two-sum/1-two-sum.js
@@ -0,0 +1,15 @@
+const twoSum = function (nums, target)
+{
+    //search of all Array
+    for (let i = 0; i < nums.length; i++)
+    {
+        for (let j = i + 1; j < nums.length; j++)
+        {
+            // if (nums[j] === target - nums[i])
+            if(nums[i] + nums[j] === target)
+            {
+                return [i, j];
+            }
+        }
+    }
+    };
\ No newline at end of file
diff --git a/1-two-sum/1-two-sum.php b/1-two-sum/1-two-sum.php
new file mode 100644
index 0000000..a1e96d4
--- /dev/null
+++ b/1-two-sum/1-two-sum.php
@@ -0,0 +1,23 @@
+<?php
+
+    class Solution {
+
+    /**
+     * @param Integer[] $nums
+     * @param Integer $target
+     * @return Integer[]
+     */
+    function twoSum($nums, $target) {
+    $map = [];
+    for ($i = 0; $i < count($nums); $i++) {
+        $complement = $target - $nums[$i];
+        if (isset($map[$complement])) {
+            return [$map[$complement], $i];
+        }
+        $map[$nums[$i]] = $i;
+    }
+}
+
+}
+
+?>
\ No newline at end of file
diff --git a/1-two-sum/1-two-sum.rb b/1-two-sum/1-two-sum.rb
new file mode 100644
index 0000000..b9c59e8
--- /dev/null
+++ b/1-two-sum/1-two-sum.rb
@@ -0,0 +1,8 @@
+def two_sum(nums, target)
+    hash = {}
+    nums.each_with_index do |num, idx|
+        complement = target - num
+        return [hash[complement], idx] if hash.key?(complement)
+        hash[num] = idx
+    end
+end
\ No newline at end of file
diff --git a/2-add-two-numbers/2-add-two-numbers.cs b/2-add-two-numbers/2-add-two-numbers.cs
new file mode 100644
index 0000000..60a03f6
--- /dev/null
+++ b/2-add-two-numbers/2-add-two-numbers.cs
@@ -0,0 +1,39 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int x) { val = x; }
+ * }
+ */
+public class Solution
+{
+    public ListNode AddTwoNumbers(ListNode l1, ListNode l2)
+    {
+        ListNode dummy = new ListNode(0);
+        ListNode current = dummy;
+        int carry = 0;
+
+        while (l1 != null || l2 != null || carry != 0)
+        {
+            int sum = carry;
+            if (l1 != null)
+            {
+                sum += l1.val;
+                l1 = l1.next;
+            }
+            if (l2 != null)
+            {
+                sum += l2.val;
+                l2 = l2.next;
+            }
+
+            carry = sum / 10;
+            sum = sum % 10;
+            current.next = new ListNode(sum);
+            current = current.next;
+        }
+
+        return dummy.next;
+    }
+}
\ No newline at end of file
diff --git a/2-add-two-numbers/2-add-two-numbers.java b/2-add-two-numbers/2-add-two-numbers.java
new file mode 100644
index 0000000..ae864e0
--- /dev/null
+++ b/2-add-two-numbers/2-add-two-numbers.java
@@ -0,0 +1,36 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        ListNode dummy = new ListNode(0);
+        ListNode current = dummy;
+        int carry = 0;
+        
+        while (l1 != null || l2 != null || carry != 0) {
+            int sum = carry;
+            if (l1 != null) {
+                sum += l1.val;
+                l1 = l1.next;
+            }
+            if (l2 != null) {
+                sum += l2.val;
+                l2 = l2.next;
+            }
+            
+            carry = sum / 10;
+            sum = sum % 10;
+            current.next = new ListNode(sum);
+            current = current.next;
+        }
+        
+        return dummy.next;
+    }
+}
\ No newline at end of file
diff --git a/2-add-two-numbers/2-add-two-numbers.js b/2-add-two-numbers/2-add-two-numbers.js
new file mode 100644
index 0000000..84505b7
--- /dev/null
+++ b/2-add-two-numbers/2-add-two-numbers.js
@@ -0,0 +1,36 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} l1
+ * @param {ListNode} l2
+ * @return {ListNode}
+ */
+var addTwoNumbers = function(l1, l2) {
+    let dummy = new ListNode(0);
+    let current = dummy;
+    let carry = 0;
+    
+    while (l1 !== null || l2 !== null || carry !== 0) {
+        let sum = carry;
+        if (l1 !== null) {
+            sum += l1.val;
+            l1 = l1.next;
+        }
+        if (l2 !== null) {
+            sum += l2.val;
+            l2 = l2.next;
+        }
+        
+        carry = Math.floor(sum / 10);
+        sum = sum % 10;
+        current.next = new ListNode(sum);
+        current = current.next;
+    }
+    
+    return dummy.next;
+};
\ No newline at end of file
diff --git a/2-add-two-numbers/2-add-two-numbers.php b/2-add-two-numbers/2-add-two-numbers.php
new file mode 100644
index 0000000..f32b781
--- /dev/null
+++ b/2-add-two-numbers/2-add-two-numbers.php
@@ -0,0 +1,46 @@
+<?php
+
+    /**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val = 0, $next = null) {
+ *         $this->val = $val;
+ *         $this->next = $next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param ListNode $l1
+     * @param ListNode $l2
+     * @return ListNode
+     */
+    function addTwoNumbers($l1, $l2) {
+        $dummy = new ListNode(0);
+        $current = $dummy;
+        $carry = 0;
+        
+        while ($l1 !== null || $l2 !== null || $carry !== 0) {
+            $sum = $carry;
+            if ($l1 !== null) {
+                $sum += $l1->val;
+                $l1 = $l1->next;
+            }
+            if ($l2 !== null) {
+                $sum += $l2->val;
+                $l2 = $l2->next;
+            }
+            
+            $carry = intdiv($sum, 10);
+            $sum = $sum % 10;
+            $current->next = new ListNode($sum);
+            $current = $current->next;
+        }
+        
+        return $dummy->next;
+    }
+}
+
+?>
\ No newline at end of file
diff --git a/2-add-two-numbers/2-add-two-numbers.rb b/2-add-two-numbers/2-add-two-numbers.rb
new file mode 100644
index 0000000..728dc52
--- /dev/null
+++ b/2-add-two-numbers/2-add-two-numbers.rb
@@ -0,0 +1,36 @@
+# Definition for singly-linked list.
+# class ListNode
+#     attr_accessor :val, :next
+#     def initialize(val = 0, _next = nil)
+#         @val = val
+#         @next = _next
+#     end
+# end
+
+# @param {ListNode} l1
+# @param {ListNode} l2
+# @return {ListNode}
+def add_two_numbers(l1, l2)
+    dummy = ListNode.new(0)
+    current = dummy
+    carry = 0
+    
+    while l1 || l2 || carry != 0
+        sum = carry
+        if l1
+            sum += l1.val
+            l1 = l1.next
+        end
+        if l2
+            sum += l2.val
+            l2 = l2.next
+        end
+        
+        carry = sum / 10
+        sum = sum % 10
+        current.next = ListNode.new(sum)
+        current = current.next
+    end
+    
+    dummy.next
+end
\ No newline at end of file
diff --git a/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.cs b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.cs
new file mode 100644
index 0000000..bbbc6f2
--- /dev/null
+++ b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.cs
@@ -0,0 +1,22 @@
+public class Solution
+{
+    public int LengthOfLongestSubstring(string s)
+    {
+        int n = s.Length;
+        HashSet<char> set = new HashSet<char>();
+        int maxLength = 0, i = 0, j = 0;
+        while (i < n && j < n)
+        {
+            if (!set.Contains(s[j]))
+            {
+                set.Add(s[j++]);
+                maxLength = Math.Max(maxLength, j - i);
+            }
+            else
+            {
+                set.Remove(s[i++]);
+            }
+        }
+        return maxLength;
+    }
+}
\ No newline at end of file
diff --git a/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.java b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.java
new file mode 100644
index 0000000..b86dd3a
--- /dev/null
+++ b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.java
@@ -0,0 +1,16 @@
+class Solution {
+    public int lengthOfLongestSubstring(String s) {
+        int n = s.length();
+        Set<Character> set = new HashSet<>();
+        int maxLength = 0, i = 0, j = 0;
+        while (i < n && j < n) {
+            if (!set.contains(s.charAt(j))) {
+                set.add(s.charAt(j++));
+                maxLength = Math.max(maxLength, j - i);
+            } else {
+                set.remove(s.charAt(i++));
+            }
+        }
+        return maxLength;
+    }
+}
\ No newline at end of file
diff --git a/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.js b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.js
new file mode 100644
index 0000000..1c9277e
--- /dev/null
+++ b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.js
@@ -0,0 +1,14 @@
+var lengthOfLongestSubstring = function(s) {
+    let n = s.length;
+    let set = new Set();
+    let maxLength = 0, i = 0, j = 0;
+    while (i < n && j < n) {
+        if (!set.has(s.charAt(j))) {
+            set.add(s.charAt(j++));
+            maxLength = Math.max(maxLength, j - i);
+        } else {
+            set.delete(s.charAt(i++));
+        }
+    }
+    return maxLength;
+};
\ No newline at end of file
diff --git a/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.php b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.php
new file mode 100644
index 0000000..ea8e77c
--- /dev/null
+++ b/3-longest-substring-without-repeating-characters/3-longest-substring-without-repeating-characters.php
@@ -0,0 +1,28 @@
+<?php
+
+    class Solution {
+
+    /**
+     * @param String $s
+     * @return Integer
+     */
+   function lengthOfLongestSubstring($s) {
+    $n = strlen($s);
+    $set = array();
+    $maxLength = 0;
+    $i = 0;
+    $j = 0;
+    while ($i < $n && $j < $n) {
+        if (!in_array($s[$j], $set)) {
+            $set[] = $s[$j++];
+            $maxLength = max($maxLength, $j - $i);
+        } else {
+            unset($set[array_search($s[$i++], $set)]);
+        }
+    }
+    return $maxLength;
+}
+
+}
+
+?>
\ No newline at end of file