Better messages when no data is found

data_structures/3_LinkedList/3_linked_lists.py

@@ -0,0 +1,158 @@
+class Node:
+    def __init__(self,val=None,next=None):
+        self.val = val 
+        self.next = next
+
+
+class LinkedList:
+    def __init__(self):
+        self.head=None
+
+    def show(self):
+        if self.head == None:
+            print('Linked List is empty')
+            return
+        else:
+            itr = self.head
+            while itr:
+                print(itr.val,' --> ',end='')
+                itr=itr.next 
+            print('None')
+
+    def getlength(self):
+        itr = self.head
+        c=0
+        while itr:
+            c+=1
+            itr = itr.next
+        return c
+
+    def insert_at_end(self,val):
+        if self.head is  None:
+            node = Node(val,None)  
+            self.head = node 
+            return
+        else:
+            itr = self.head
+            while itr.next :
+                itr=itr.next
+            itr.next=Node(val,None)
+
+    def insert_at_beginning(self,val):
+        node = Node(val,self.head)
+        self.head=node 
+
+    def insert_values(self,x):
+        self.head = None
+        for d in x:
+            self.insert_at_end(d)
+
+    def insert_at_pos(self,pos,val):
+        if pos < 0 or pos >= self.getlength():
+            raise Exception("Invalid syntax")
+
+        if pos == 0:
+            self.insert_at_beginning(val)
+            return 
+        elif pos == self.getlength() - 1:
+            self.insert_at_end(val)
+            return
+        else:
+            itr = self.head
+            c = 0
+            while itr:
+                if c==pos -1:
+                    node = Node(val,itr.next)
+                    itr.next=node 
+                    break
+                c+=1
+                itr = itr.next
+
+    def remove_at_pos(self,pos):
+        if pos < 0 or pos >= self.getlength():
+            raise Exception('Invalid position')
+        if pos ==0:
+            self.head=self.head.next
+            return
+        itr = self.head
+        c=0
+        while itr:
+            if c==pos-1:
+                itr.next=itr.next.next
+                break
+            c+=1
+            itr=itr.next
+        pass
+    # Adding for task
+    def insert_after_value(self,val_before,val):
+        if self.head is None:
+            return
+
+        if self.head.val==val_before:
+            self.head.next = Node(val,self.head.next)
+            return
+
+        itr=self.head
+        c=0
+        while itr:
+            if val_before==itr.val:
+                self.insert_at_pos(c+1,val)
+                break
+            c+=1
+            itr=itr.next
+        else:
+            print('Data is not in the linked list')
+
+    def remove_by_val(self,val):
+        if self.head is None:
+            return
+
+        if self.head.val == val:
+            self.head = self.head.next
+            return
+
+        itr=self.head
+        c=0
+        while itr:
+            if itr.val == val:
+                self.remove_at_pos(c)
+                break
+            itr=itr.next
+            c+=1
+        else:
+            print('No such value present in linked list')
+
+
+
+if __name__ == '__main__':
+    '''
+    l=LinkedList()
+    l.insert_values(['A','B','C','D'])
+    l.show()
+    l.insert_at_pos(2,'F')
+    l.show()
+    l.remove_at_pos(3)
+    l.show()
+    l.insert_at_end('R')
+    l.show()
+    l.insert_at_beginning('J')
+    l.show()
+    l.insert_after_value('A','K')
+    l.show()
+    l.remove_by_val('K')
+    l.show()
+    '''
+    ll = LinkedList()
+    ll.insert_values(["banana","mango","grapes","orange"])
+    ll.show()
+    ll.insert_after_value("mango","apple") # insert apple after mango
+    ll.show()
+    ll.remove_by_val("orange") # remove orange from linked list
+    ll.show()
+    ll.remove_by_val("figs")
+    ll.show()
+    ll.remove_by_val("banana")
+    ll.remove_by_val("mango")
+    ll.remove_by_val("apple")
+    ll.remove_by_val("grapes")
+    ll.show()