# Delete all the nodes from the list that are greater than x

Given a linked list, the problem is to delete all the nodes from the list that are greater than the specified value **x**.

Examples:

Input : list: 7->3->4->8->5->1 x = 6 Output : 3->4->5->1 Input : list: 1->8->7->3->7->10 x = 7 Output : 1->7->3->7

**Source: **Microsoft Interview Experience | Set 169.

**Approach:** This is mainly a variation of the post which deletes first occurrence of a given key.

We need to first check for all occurrences at head node which are greater than ‘x’, delete them and change the head node appropriately. Then we need to check for all occurrences inside a loop and delete them one by one.

`// C++ implementation to delete all the nodes from the list ` `// that are greater than the specified value x ` `#include <bits/stdc++.h> ` ` ` `using` `namespace` `std; ` ` ` `// structure of a node ` `struct` `Node { ` ` ` `int` `data; ` ` ` `Node* next; ` `}; ` ` ` `// function to get a new node ` `Node* getNode(` `int` `data) ` `{ ` ` ` `Node* newNode = ` `new` `Node; ` ` ` `newNode->data = data; ` ` ` `newNode->next = NULL; ` ` ` `return` `newNode; ` `} ` ` ` `// function to delete all the nodes from the list ` `// that are greater than the specified value x ` `void` `deleteGreaterNodes(Node** head_ref, ` `int` `x) ` `{ ` ` ` `Node *temp = *head_ref, *prev; ` ` ` ` ` `// If head node itself holds the value greater than 'x' ` ` ` `if` `(temp != NULL && temp->data > x) { ` ` ` `*head_ref = temp->next; ` `// Changed head ` ` ` `free` `(temp); ` `// free old head ` ` ` `temp = *head_ref; ` `// Change temp ` ` ` `} ` ` ` ` ` `// Delete occurrences other than head ` ` ` `while` `(temp != NULL) { ` ` ` ` ` `// Search for the node to be deleted, ` ` ` `// keep track of the previous node as we ` ` ` `// need to change 'prev->next' ` ` ` `while` `(temp != NULL && temp->data <= x) { ` ` ` `prev = temp; ` ` ` `temp = temp->next; ` ` ` `} ` ` ` ` ` `// If required value node was not present ` ` ` `// in linked list ` ` ` `if` `(temp == NULL) ` ` ` `return` `; ` ` ` ` ` `// Unlink the node from linked list ` ` ` `prev->next = temp->next; ` ` ` ` ` `delete` `temp; ` `// Free memory ` ` ` ` ` `// Update Temp for next iteration of ` ` ` `// outer loop ` ` ` `temp = prev->next; ` ` ` `} ` `} ` ` ` `// function to a print a linked list ` `void` `printList(Node* head) ` `{ ` ` ` `while` `(head) { ` ` ` `cout << head->data << ` `" "` `; ` ` ` `head = head->next; ` ` ` `} ` `} ` ` ` `// Driver program to test above ` `int` `main() ` `{ ` ` ` `// Create list: 7->3->4->8->5->1 ` ` ` `Node* head = getNode(7); ` ` ` `head->next = getNode(3); ` ` ` `head->next->next = getNode(4); ` ` ` `head->next->next->next = getNode(8); ` ` ` `head->next->next->next->next = getNode(5); ` ` ` `head->next->next->next->next->next = getNode(1); ` ` ` ` ` `int` `x = 6; ` ` ` ` ` `cout << ` `"Original List: "` `; ` ` ` `printList(head); ` ` ` ` ` `deleteGreaterNodes(&head, x); ` ` ` ` ` `cout << ` `"\nModified List: "` `; ` ` ` `printList(head); ` ` ` ` ` `return` `0; ` `} ` |

Output:

Original List: 7 3 4 8 5 1 Modified List: 3 4 5 1

Time Complexity: O(n).