Leetcode Same Tree Iterative Solution

Question

Question at hand: https://leetcode.com/problems/same-tree/

Can someone point out why my JavaScript solution can pass the test cases but fails during the actual submission?

var isSameTree = function(p, q) {
  let queue = [];
  queue.push(p);
  queue.push(q);
  while (!queue.length) {
    let p = queue.shift();
    let q = queue.shift();

    if (p == null && q == null) {
      continue;
    } else if (p == null || q == null || p.val != q.val) {
      return false;
    } else {
      queue.push(p.left);
      queue.push(q.left);
      queue.push(p.right);
      queue.push(q.right);
    }
  }
  return true;
};

Essentially you need to traverse both trees. so you have to write your function recursively some way. your current implementation just checks the equality of trees' roots and nothing more. — Mahdi Ghajary, Nov 02 '20 at 13:09
But isn't that why I have this line in case the values do not match: else if (p == null || q == null || p.val != q.val) { return false; } — Mike Chan, Nov 02 '20 at 13:17
Imagine both trees have a root with value of `3`. what happens next? — Mahdi Ghajary, Nov 02 '20 at 13:21
The `while` condition is such that it never gets into the loop. Typo... ;-) — trincot, Nov 02 '20 at 13:21

score 0 · Answer 1 · answered Nov 02 '20 at 13:30

@trincot mentioned it in the comments.

Just update the comparison inside the while loop to get into that loop.

var isSameTree = function(p, q) {
  let queue = [];
  queue.push(p);
  queue.push(q);
  while (queue.length != 0) {
    let p = queue.shift();
    let q = queue.shift();

    if (p == null && q == null) {
      continue;
    } else if (p == null || q == null || p.val != q.val) {
      return false;
    } else {
      queue.push(p.left);
      queue.push(q.left);
      queue.push(p.right);
      queue.push(q.right);
    }
  }
  console.log(queue);
  return true;
};

This will pass all the test cases.

Leetcode Same Tree Iterative Solution

1 Answers1