diff --git a/Longest_Substring_Without_Repeating_Characters.rb b/Longest_Substring_Without_Repeating_Characters.rb
new file mode 100644
index 0000000..eceb843
--- /dev/null
+++ b/Longest_Substring_Without_Repeating_Characters.rb
@@ -0,0 +1,16 @@
+# @param {String} s
+# @return {Integer}
+def length_of_longest_substring(s)
+    stack = []
+  highest_count = 0
+  s.each_char do |c|
+    unless index = stack.index(c)
+      stack.push(c)
+    else
+      stack.push(c)
+      (index + 1).times {stack.shift}
+    end
+    highest_count = stack.length if stack.length > highest_count
+  end
+  highest_count
+end
diff --git a/Max_Area_of_Island.rb b/Max_Area_of_Island.rb
new file mode 100644
index 0000000..3f9353d
--- /dev/null
+++ b/Max_Area_of_Island.rb
@@ -0,0 +1,23 @@
+def DFS(grid, i, j)
+    if i < 0 || j < 0 || i > grid.length - 1 || j > grid[0].length - 1 || grid[i][j] == 0
+        return 0
+    end
+    
+    grid[i][j] = 0
+    
+    return 1 + DFS(grid, i - 1, j) + DFS(grid, i + 1, j) + DFS(grid, i, j - 1) + DFS(grid, i, j + 1)
+end
+
+# @param {Integer[][]} grid
+# @return {Integer}
+def max_area_of_island(grid)
+    maxArea = 0
+    
+    for i in 0..grid.length - 1
+        for j in 0..grid[0].length - 1
+            maxArea = [maxArea, DFS(grid, i, j)].max
+        end
+    end
+    
+    return maxArea
+end
diff --git a/MiddleoftheLinkedList.rb b/MiddleoftheLinkedList.rb
new file mode 100644
index 0000000..59dea9f
--- /dev/null
+++ b/MiddleoftheLinkedList.rb
@@ -0,0 +1,17 @@
+def middle_node(head)
+    org_head = head
+    count = 0
+    while !head.nil?
+        count+=1
+        head = head.next
+    end
+    
+    i = 0
+    head = org_head
+    while i < count/2
+        i+=1
+        head = head.next
+    end
+    
+    return head
+end
diff --git a/Permutation_in_String.rb b/Permutation_in_String.rb
new file mode 100644
index 0000000..cb3f838
--- /dev/null
+++ b/Permutation_in_String.rb
@@ -0,0 +1,23 @@
+# @param {String} s1
+# @param {String} s2
+# @return {Boolean}
+def check_inclusion(s1, s2)
+    return false if s2.size < s1.size
+    window = Array.new(26, 0) 
+    
+    s1.each_char do |ch|
+        window[ch.ord - 'a'.ord] += 1
+    end
+    
+    s2.each_char.with_index do |ch, i|
+        window[ch.ord - 'a'.ord] -= 1
+        if i >= s1.size
+            window[s2[i - s1.size].ord - 'a'.ord] += 1
+        end
+        if window.all?(&:zero?)
+            return true
+        end
+    end
+    
+    false
+end
diff --git a/Remove_Nth_Node_From_End_of_List.rb b/Remove_Nth_Node_From_End_of_List.rb
new file mode 100644
index 0000000..5f2a4ca
--- /dev/null
+++ b/Remove_Nth_Node_From_End_of_List.rb
@@ -0,0 +1,17 @@
+def remove_nth_from_end(head, n)
+   node = head
+    prev = nil
+    arr_node = []
+    while !node.nil? do
+        arr_node << node
+        node = node.next
+    end
+    if arr_node.length - n == 0
+        head = head.next
+    else 
+        node = arr_node[-n-1]
+        node.next = node.next.next
+    end
+    
+    return head
+end
diff --git a/ReverseWordsinaStringIII.rb b/ReverseWordsinaStringIII.rb
new file mode 100644
index 0000000..723b642
--- /dev/null
+++ b/ReverseWordsinaStringIII.rb
@@ -0,0 +1,3 @@
+def reverse_words(s)
+      s.split.map(&:reverse).join(" ")
+end
diff --git a/merge_two_lists.rb b/merge_two_lists.rb
new file mode 100644
index 0000000..1cf13ac
--- /dev/null
+++ b/merge_two_lists.rb
@@ -0,0 +1,47 @@
+# Definition for singly-linked list.
+# class ListNode
+#     attr_accessor :val, :next
+#     def initialize(val)
+#         @val = val
+#         @next = nil
+#     end
+# end
+
+# @param {ListNode} l1
+# @param {ListNode} l2
+# @return {ListNode}
+def merge_two_lists(l1, l2)
+    solution = [] # head = nil
+    ho = l1
+    ht = l2
+    
+    while !ho.nil? && !ht.nil? do  
+        if ho.val < ht.val
+            solution << ho.val
+            ho = ho.next
+        else
+            solution << ht.val
+            ht = ht.next
+        end
+    end
+    
+    if ho.nil?
+        while !ht.nil? do 
+            solution << ht.val
+            ht = ht.next
+        end
+    elsif ht.nil? 
+        while !ho.nil? do 
+            solution << ho.val
+            ho = ho.next
+        end
+    end 
+    
+    solution
+end
+
+list1 = [1,2,4], list2 = [1,3,4]
+
+re = merge_two_lists(list1, list2)
+
+puts re
\ No newline at end of file
diff --git a/remove_element.rb b/remove_element.rb
new file mode 100644
index 0000000..dde2a71
--- /dev/null
+++ b/remove_element.rb
@@ -0,0 +1,19 @@
+# @param {Integer[]} nums
+# @param {Integer} val
+# @return {Integer}
+def remove_element(nums, val)
+    return 0 if nums.length == 0
+     nums.each_with_index do |num, index|
+         if num == val
+             nums[index] = nil
+         end
+     end
+     nums.compact!
+     nums.length
+     
+ end
+
+
+nums = [3,2,2,3], val = 3
+
+puts remove_element(nums,val)
\ No newline at end of file