added reverseLinkedList

Author: sushant097

LinkedList/ReverseLinkedList.py

@@ -0,0 +1,143 @@
+# Reverse the given linkedlist
+
+
+def reverse_iterative(self):
+    prev = None
+    cur = self.head
+    while cur:
+        next_node = cur.next
+        cur.next = prev
+        prev = cur
+        cur = cur.next
+        
+    self.head = prev
+    
+
+class Node:
+    def __init__(self, data):
+        self.data = data
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+
+    def print_list(self):
+        cur_node = self.head
+        while cur_node:
+            print(cur_node.data)
+            cur_node = cur_node.next
+
+    def append(self, data):
+        new_node = Node(data)
+
+        if self.head is None:
+            self.head = new_node
+            return
+
+        last_node = self.head
+        while last_node.next:
+            last_node = last_node.next
+        last_node.next = new_node
+
+    def prepend(self, data):
+        new_node = Node(data)
+
+        new_node.next = self.head
+        self.head = new_node
+
+    def insert_after_node(self, prev_node, data):
+
+        if not prev_node:
+            print("Previous node does not exist.")
+            return 
+
+        new_node = Node(data)
+
+        new_node.next = prev_node.next
+        prev_node.next = new_node
+
+    def delete_node(self, key):
+
+        cur_node = self.head
+
+        if cur_node and cur_node.data == key:
+            self.head = cur_node.next
+            cur_node = None
+            return
+
+        prev = None 
+        while cur_node and cur_node.data != key:
+            prev = cur_node
+            cur_node = cur_node.next
+
+        if cur_node is None:
+            return 
+
+        prev.next = cur_node.next
+        cur_node = None
+
+    def delete_node_at_pos(self, pos):
+        if self.head:
+            cur_node = self.head
+
+            if pos == 0:
+                self.head = cur_node.next
+                cur_node = None
+                return
+
+            prev = None
+            count = 1
+            while cur_node and count != pos:
+                prev = cur_node 
+                cur_node = cur_node.next
+                count += 1
+
+            if cur_node is None:
+                return 
+
+            prev.next = cur_node.next
+            cur_node = None
+
+    def len_iterative(self):
+
+        count = 0
+        cur_node = self.head
+
+        while cur_node:
+            count += 1
+            cur_node = cur_node.next
+        return count
+
+    def len_recursive(self, node):
+        if node is None:
+            return 0
+        return 1 + self.len_recursive(node.next)
+
+    def print_helper(self, node, name):
+        if node is None:
+            print(name + ": None")
+        else:
+            print(name + ":" + node.data)
+
+    def reverse_iterative(self):
+
+        prev = None 
+        cur = self.head
+        while cur:
+            nxt = cur.next
+            cur.next = prev
+            prev = cur 
+            cur = nxt 
+        self.head = prev
+        
+llist = LinkedList()
+llist.append("A")
+llist.append("B")
+llist.append("C")
+llist.append("D")
+
+llist.reverse_iterative()
+
+llist.print_list()