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Leetcode diary: 1261. Find Elements in a Contaminated Binary Tree

This is a new series where I document my struggles of leetcode questions hoping seeing however small of an audience I get gives me the motivation to continue.

This problem is relatively simple, but a small trick can speed up the performance well. I believe if you know how to do BFS to traverse the tree then you should have no problem adding values to the tree.

Below is my code:

var FindElements = function(root) {
    root.val = 0;
    const stack = [root];
    let current;
    const record = new Set();

    while (stack.length) {
        current = stack.shift();
        if (current.left)  { 
            current.left.val = getLeft(current.val); 
        if (current.right) { 
            current.right.val = getRight(current.val); 

    this.record = record;

    function getLeft  (num) { return 2 * num + 1; }
    function getRight (num) { return 2 * num + 2; }

FindElements.prototype.find = function(target) {
    return this.record.has(target);

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I did not think of using a set for my answer, this was suggested by a better performance solution. Pretty neat, might come in handy one day for me.

Let me know anything on your mind after reading through this, THANKS!

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