Given a singly linked list where each node represents a character including special characters, the task is to remove all the occurrences of special characters from the linked list so that only valid characters are present in the linked list.
Examples:
Input: List = ( -> G -> E -> E -> * -> K -> S -> * -> NULL
Output: G -> E -> E -> K -> S -> NULLInput: A -> B -> C -> * -> @ -> NULL
Output: A -> B -> C -> NULL
Approach: Traverse the linked list, if the current node’s data is a special character then make the next of the previous node point to the next of the current node. Do this for every node with a special character and finally print the updated list.
Below is the implementation of the above approach:
C++
// C++ implementation of the approach #include <iostream> using namespace std; // Structure for the node // of the linked list struct node { char data; node* next; }; // Utility function to add a new // node to the linked list node* add(char data) { node* newnode = new node; // Assign the data to the data part // and assign NULL to the address part newnode->data = data; newnode->next = NULL; return newnode; } // Function to print the linked list void print(node* head) { while (head != NULL) { cout << head->data << " -> "; head = head->next; } cout << "NULL"; } // Function that returns true if // ch is a special character bool isSpecialChar(char ch) { // If lower-case character if (ch >= 'a' && ch <= 'z') return false; // If upper-case character if (ch >= 'A' && ch <= 'Z') return false; // If digit if (ch >= '0' && ch <= '9') return false; // ch is a special character return true; } // Function to remove the special // characters from the linked list node* removeFromLL(node* head) { // Declare two variables curr and // prev both pointing to head node *curr = head, *prev = head; // The following loop removes special // characters from the head of the linked list // In case the special character is present at // the head of the linked list, make head point // to the next valid character while (curr != NULL && isSpecialChar(curr->data)) { node* temp = curr; head = curr->next; curr = curr->next; delete temp; } // Make prev point to head prev = head; // Repeat the process for // the entire Linked list while (curr != NULL) { // Repeat the process for all the elements // of linked list, in case a special character // is encountered then make the previous valid // character point to the next valid character // and remove the current node from the linked list while (curr != NULL && isSpecialChar(curr->data)) { node* temp = curr; prev->next = curr->next; curr = curr->next; delete temp; } // If the end is reached if (curr == NULL) break; prev = curr; curr = curr->next; } return head; } // Driver code int main() { // Create the linked list node* head = NULL; head = add('('); head->next = add('G'); head->next->next = add('E'); head->next->next->next = add('E'); head->next->next->next->next = add('*'); head->next->next->next->next->next = add('K'); head->next->next->next->next->next->next = add('S'); head->next->next->next->next->next->next->next = add('*'); // Remove the special characters // from the linked list head = removeFromLL(head); // Print the updated list print(head); return 0; } |
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Java
// Java implementation of the approach class GFG { // Structure for the node // of the linked list static class node { char data; node next; }; // Utility function to add a new // node to the linked list static node add(char data) { node newnode = new node(); // Assign the data to the data part // and assign null to the address part newnode.data = data; newnode.next = null; return newnode; } // Function to print the linked list static void print(node head) { while (head != null) { System.out.print(head.data + " -> "); head = head.next; } System.out.print("null"); } // Function that returns true if // ch is a special character static boolean isSpecialChar(char ch) { // If lower-case character if (ch >= 'a' && ch <= 'z') return false; // If upper-case character if (ch >= 'A' && ch <= 'Z') return false; // If digit if (ch >= '0' && ch <= '9') return false; // ch is a special character return true; } // Function to remove the special // characters from the linked list static node removeFromLL(node head) { // Declare two variables curr and // prev both pointing to head node curr = head; node prev = head; // The following loop removes special // characters from the head of the linked list // In case the special character is present at // the head of the linked list, make head point // to the next valid character while (curr != null && isSpecialChar(curr.data)) { node temp = curr; head = curr.next; curr = curr.next; temp = null; } // Make prev point to head prev = head; // Repeat the process for // the entire Linked list while (curr != null) { // Repeat the process for all the elements // of linked list, in case a special character // is encountered then make the previous valid // character point to the next valid character // and remove the current node from the linked list while (curr != null && isSpecialChar(curr.data)) { node temp = curr; prev.next = curr.next; curr = curr.next; temp = null; } // If the end is reached if (curr == null) break; prev = curr; curr = curr.next; } return head; } // Driver code public static void main(String[] args) { // Create the linked list node head = null; head = add('('); head.next = add('G'); head.next.next = add('E'); head.next.next.next = add('E'); head.next.next.next.next = add('*'); head.next.next.next.next.next = add('K'); head.next.next.next.next.next.next = add('S'); head.next.next.next.next.next.next.next = add('*'); // Remove the special characters // from the linked list head = removeFromLL(head); // Print the updated list print(head); } } // This code is contributed by PrinciRaj1992 |
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Python3
# Python3 implementation of the approach import math # Structure for the node # of the linked list class Node: def __init__(self, data): self.data = data self.next = None # Utility function to add a new # node to the linked list def add(data): newnode = Node(data) # Assign the data to the data part # and assign None to the address part newnode.data = data newnode.next = None return newnode # Function to print the linked list def printlist(head): while (head != None) : print(head.data, end = " -> ") head = head.next print("None") # Function that returns true if # ch is a special character def isSpecialChar(ch): # If lower-case character if (ch >= 'a' and ch <= 'z'): return False # If upper-case character if (ch >= 'A' and ch <= 'Z'): return False # If digit if (ch >= '0' and ch <= '9'): return False # ch is a special character return True # Function to remove the special # characters from the linked list def removeFromLL(head): # Declare two variables curr and # prev both pointing to head curr = head prev = head # The following loop removes special # characters from the head of the linked list # In case the special character is present at # the head of the linked list, make head point # to the next valid character while (curr != None and isSpecialChar(curr.data)): temp = curr head = curr.next curr = curr.next temp = None # Make prev point to head prev = head # Repeat the process for # the entire Linked list while (curr != None): # Repeat the process for all the elements # of linked list, in case a special character # is encountered then make the previous valid # character point to the next valid character # and remove the current node from the linked list while (curr != None and isSpecialChar(curr.data)): temp = curr prev.next = curr.next curr = curr.next temp = None # If the end is reached if (curr == None): break prev = curr curr = curr.next return head # Driver code if __name__=='__main__': # Create the linked list head = None head = add('(') head.next = add('G') head.next.next = add('E') head.next.next.next = add('E') head.next.next.next.next = add('*') head.next.next.next.next.next = add('K') head.next.next.next.next.next.next = add('S') head.next.next.next.next.next.next.next = add('*') # Remove the special characters # from the linked list head = removeFromLL(head) # Print the updated list printlist(head) # This code is contributed by Srathore |
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C#
// C# implementation of the approach using System; class GFG { // Structure for the node // of the linked list class node { public char data; public node next; }; // Utility function to add a new // node to the linked list static node add(char data) { node newnode = new node(); // Assign the data to the data part // and assign null to the address part newnode.data = data; newnode.next = null; return newnode; } // Function to print the linked list static void print(node head) { while (head != null) { Console.Write(head.data + " -> "); head = head.next; } Console.Write("null"); } // Function that returns true if // ch is a special character static Boolean isSpecialChar(char ch) { // If lower-case character if (ch >= 'a' && ch <= 'z') return false; // If upper-case character if (ch >= 'A' && ch <= 'Z') return false; // If digit if (ch >= '0' && ch <= '9') return false; // ch is a special character return true; } // Function to remove the special // characters from the linked list static node removeFromLL(node head) { // Declare two variables curr and // prev both pointing to head node curr = head; node prev = head; // The following loop removes special // characters from the head of the linked list // In case the special character is present at // the head of the linked list, make head point // to the next valid character while (curr != null && isSpecialChar(curr.data)) { node temp = curr; head = curr.next; curr = curr.next; temp = null; } // Make prev point to head prev = head; // Repeat the process for // the entire Linked list while (curr != null) { // Repeat the process for all the elements // of linked list, in case a special character // is encountered then make the previous valid // character point to the next valid character // and remove the current node from the linked list while (curr != null && isSpecialChar(curr.data)) { node temp = curr; prev.next = curr.next; curr = curr.next; temp = null; } // If the end is reached if (curr == null) break; prev = curr; curr = curr.next; } return head; } // Driver code public static void Main(String[] args) { // Create the linked list node head = null; head = add('('); head.next = add('G'); head.next.next = add('E'); head.next.next.next = add('E'); head.next.next.next.next = add('*'); head.next.next.next.next.next = add('K'); head.next.next.next.next.next.next = add('S'); head.next.next.next.next.next.next.next = add('*'); // Remove the special characters // from the linked list head = removeFromLL(head); // Print the updated list print(head); } } // This code is contributed by PrinciRaj1992 |
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Output:
G -> E -> E -> K -> S -> NULL
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