Central Linked List - Amazon Top Interview Questions


Problem Statement :


Given a singly linked list node, return the value of the middle node. If there's two middle nodes, then return the second one.

Bonus: Solve using \mathcal{O}(1)O(1) space.

Constraints

n ≤ 100,000 where n is the number of nodes in node

Example 1

Input

node = [0, 1, 2]

Output

1


Solution :



title-img



                        Solution in C++ :

int solve(LLNode* node) {
    LLNode *fast = node, *slow = node;
    while (fast != NULL && fast->next != NULL) {
        slow = slow->next;
        fast = fast->next->next;
    }
    return slow->val;
}
                    

                        Solution in Java :

import java.util.*;

/**
 * class LLNode {
 *   int val;
 *   LLNode next;
 * }
 */
class Solution {
    public int solve(LLNode node) {
        LLNode slow = node;
        LLNode fast = node;

        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow.val;
    }
}
                    

                        Solution in Python : 
                            
class Solution:
    def solve(self, node):
        slow = node
        fast = node
        while fast != None and fast.next != None:
            slow = slow.next
            fast = fast.next.next
        return slow.val
                    

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