Learn AI Create the Future — with Pranay
Main site

LeetCode solutions

116. Populating Next Right Pointers in Each Node

My accepted JavaScript solution to LeetCode problem 116, Populating Next Right Pointers in Each Node, running in 48ms.

  • Difficulty: Medium
  • JavaScript
  • Runtime 48ms
  • Memory 60MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

JavaScript

Accepted on LeetCode — runtime 48ms, memory 60MB, accepted 2025-12-24.

javascript
/**
 * @param {Node} root
 * @return {Node}
 */
var connect = function(root) {
    if (!root) return null;
    
    let leftmost = root;
    
    // Level by level using next pointers (O(1) space)
    while (leftmost.left) {
        let curr = leftmost;
        
        while (curr) {
            // Connect left to right within same parent
            curr.left.next = curr.right;
            
            // Connect right to next parent's left
            if (curr.next) {
                curr.right.next = curr.next.left;
            }
            
            curr = curr.next;
        }
        
        leftmost = leftmost.left;
    }
    
    return root;
};

Source