Insert Into Linked List - Facebook Top Interview Questions
Problem Statement :
You are given a singly linked list head as well as integers pos and val. Insert a new node with value val before index pos of head. Constraints 1 ≤ n ≤ 100,000 where n is the number of nodes in head 0 ≤ pos ≤ n Example 1 Input head = [1, 3, 5, 7] pos = 2 val = 9 Output [1, 3, 9, 5, 7] Example 2 Input head = [1] pos = 0 val = 3 Output [3, 1] Example 3 Input head = [2] pos = 1 val = 5 Output [2, 5]
Solution :
Solution in C++ :
LLNode* solve(LLNode* head, int pos, int val) {
auto dum = new LLNode(-1, head), prev = dum;
while (pos--) {
prev = head;
head = head->next;
}
LLNode* temp = new LLNode(val, head);
prev->next = temp;
return dum->next;
}
Solution in Java :
import java.util.*;
/**
* class LLNode {
* int val;
* LLNode next;
* }
*/
class Solution {
public LLNode solve(LLNode head, int pos, int val) {
if (pos == 0) {
LLNode ans = new LLNode(val, head);
return ans;
}
LLNode temp = head;
while (pos > 1) {
temp = temp.next;
pos--;
}
temp.next = new LLNode(val, temp.next);
return head;
}
}
Solution in Python :
class Solution:
def solve(self, head, pos, val):
new = LLNode(val)
if pos == 0:
new.next = head
return new
temp = head
while temp and pos != 1:
temp = temp.next
pos -= 1
new.next = temp.next
temp.next = new
return head
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