967. Insertion before the value X in Linked List

Given the head of a singly linked list and two integers X and val.

Insert a node with value val before the node with value X in the linked list and return the head of the modified list.

Example 1:

Input: linkedList = [1, 2, 3], X = 2, val = 5

Output: [1, 5, 2, 3]

Explanation:

The node with value 5 was added before the node with value 2

Example 2:

Input: linkedList = [1, 2, 3], X = 7, val = 5

Output: [1, 2, 3]

Explanation:

No node was added as X was not found in the list.

Now Your Turn!

Pick the correct output for the given input

Input: linkedList = [1], X = 1, val = 10

Still unsure what the problem is asking ?

Let’s go through a few more examples, step by step, to make it clearer.

Constraints:

  • n == number of nodes in the Linked List
  • 1 <= n <= 1000
  • 0 <= ListNode.val <= 100
  • 0 <= X <= 100
  • 0 <= val <= 100
  • Number of nodes with value X is 0 or 1

Hints

Frequently Occurring Doubts

Interview Follow-up Questions

0
/*
Definition of singly linked list:
class ListNode{
public:
int data;
ListNode *next;
ListNode() : data(0), next(nullptr) {}
ListNode(int x) : data(x), next(nullptr) {}
ListNode(int x, ListNode *next) : data(x), next(next) {}
};
*/
 
class Solution {
public:
ListNode* insertBeforeX(ListNode* &head, int X, int val) {
//your code goes here
}
};
Test Case

Input:

X
Linked List
Val
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