From 000a66d8be2843bdc0b9718a48c3c42d45a969ce Mon Sep 17 00:00:00 2001
From: Hanh Solo <minhhanhnyc@gmail.com>
Date: Sun, 18 Apr 2021 21:33:02 -0700
Subject: [PATCH] Linkedlist submission

---
 lib/linked_list.rb | 183 +++++++++++++++++++++++++++++++++------------
 1 file changed, 136 insertions(+), 47 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 5e173ebc..d9efd826 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -18,97 +18,160 @@ def initialize
 
     # method to add a new node with the specific data value in the linked list
     # insert the new node at the beginning of the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(1)
+    # Space Complexity: O(1)
     def add_first(value)
-      raise NotImplementedError
+      new_node = Node.new(value, nil)
+      new_node.next = @head
+      @head = new_node
     end
 
     # method to find if the linked list contains a node with specified value
     # returns true if found, false otherwise
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def search(value)
-      raise NotImplementedError
+      current = @head
+
+      while current !=nil
+        if current.data == value
+          return true
+        end
+        current = current.next
+      end
+
+      return false
     end
 
     # method to return the max value in the linked list
     # returns the data value and not the node
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def find_max
-      raise NotImplementedError
+      return if @head == nil
+
+      current = @head
+      max = current.data
+
+      while current.next != nil
+        if max < current.next.data
+          max = current.next.data
+        end
+        current = current.next
+      end
+
+      return max
+
     end
 
     # method to return the min value in the linked list
     # returns the data value and not the node
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def find_min
-      raise NotImplementedError
-    end
+      return if @head == nil
 
+      current = @head
+      min = current.data
 
-    # Additional Exercises 
-    # returns the value in the first node
-    # returns nil if the list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def get_first
-      raise NotImplementedError
-    end
+      while current.next != nil
+        if current.next.data < min
+          min = current.next.data
+        end
+        current = current.next
+      end
 
-    # method that inserts a given value as a new last node in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def add_last(value)
-      raise NotImplementedError
+      return min
     end
 
+
     # method that returns the length of the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def length
-      raise NotImplementedError
+      current = @head
+      count = 0
+      while current !=nil
+        current = current.next
+        count += 1
+      end
+      return count
     end
 
     # method that returns the value at a given index in the linked list
     # index count starts at 0
     # returns nil if there are fewer nodes in the linked list than the index value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def get_at_index(index)
-      raise NotImplementedError
+      current = @head
+      count = 0
+      while current !=nil
+        if index == count
+          return current.data
+        end
+        current = current.next
+        count += 1
+      end
+      return nil
     end
 
     # method to print all the values in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def visit
-      raise NotImplementedError
+      return if @head == nil
+      current = @head
+
+      while current.next !=nil
+        current = current.next
+        print current.data
+      end
     end
 
     # method to delete the first node found with specified value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def delete(value)
-      raise NotImplementedError
+      return 0 if @head == nil
+
+      current = @head
+      if current.data == value
+        @head = current.next
+        return
+      end
+
+      while current.next != nil
+        if current.next.data == value
+          current.next = current.next.next
+          return
+        end
+        current = current.next
+      end
+      
     end
 
     # method to reverse the singly linked list
     # note: the nodes should be moved and not just the values in the nodes
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def reverse
-      raise NotImplementedError
-    end
+      return if @head == nil
+      current = @head
+      previous = nil
+      
+      while !current.nil?
+        next_node = current.next
+        current.next = previous
+        previous = current
+        current = next_node
+      end
+
+      @head = previous
 
-    # method that returns the value of the last node in the linked list
-    # returns nil if the linked list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def get_last
-      raise NotImplementedError
     end
-  
+
+
     ## Advanced Exercises
     # returns the value at the middle element in the singly linked list
     # Time Complexity: ?
@@ -134,6 +197,32 @@ def has_cycle
       raise NotImplementedError
     end
 
+
+    # Additional Exercises 
+    # returns the value in the first node
+    # returns nil if the list is empty
+    # Time Complexity: ?
+    # Space Complexity: ?
+    def get_first
+      return if @head == nil
+      return @head.value
+    end
+
+    # method that inserts a given value as a new last node in the linked list
+    # Time Complexity: ?
+    # Space Complexity: ?
+    def add_last(value)
+      raise NotImplementedError
+    end
+
+    # method that returns the value of the last node in the linked list
+    # returns nil if the linked list is empty
+    # Time Complexity: ?
+    # Space Complexity: ?
+    def get_last
+      raise NotImplementedError
+    end
+
     # method to insert a new node with specific data value, assuming the linked
     # list is sorted in ascending order
     # Time Complexity: ?