binary-tree – JSAlgorithm

Path Sum II

Ron — Sun, 17 May 2020 02:54:10 +0000

let pathSum = function(root, sum, results = [], result = []) {

    if (!root) return results;
    if (sum - root.val === 0 && !root.left && !root.right) {
        results.push([...result, root.val]);
    }

    pathSum(root.left, sum - root.val, results, [...result, root.val]);
    pathSum(root.right, sum - root.val, results, [...result, root.val]);
    return results;
};

Path Sum I

Ron — Sun, 17 May 2020 02:38:24 +0000

let hasPathSum = function(root, sum) {

    if (!root) return false;
    if (sum - root.val === 0 && !root.left && !root.right) return true;

    return hasPathSum(root.left, sum - root.val)
        || hasPathSum(root.right, sum - root.val);
};

Is Subtree

Ronald — Thu, 14 May 2020 03:45:03 +0000

let isSubtree = function(mainTree, subTree) {

    function isSame(left, right) {
        if (left === right) return true;
        if (left === null && right !== null) return false;
        if (left !== null && right === null) return false;
        if (left.val !== right.val) return false;
        return isSame(left.left, right.left)
            && isSame(left.right, right.right);
    }

    if (mainTree === subTree) return true;
    if (!mainTree) return false;
    if (isSame(mainTree, subTree)) return true;

    return isSubtree(mainTree.left, subTree) || isSubtree(mainTree.right, subTree);
};

Level Order ZigZag Traversal

Ronald — Tue, 12 May 2020 19:50:55 +0000

function levelOrderZigzag(root) {

    let queue = [root], result = [], direction = 0;
    function process(node) {
        result.push(node.val); //?
    }

    while (queue.length) {
        let level = [];
        while(queue.length) {
            const node = queue.pop();
            process(node);
            if (direction === 0) {
                if (node.left) level.push(node.left);
                if (node.right) level.push(node.right);
            }
            else {
                if (node.right) level.push(node.right);
                if (node.left) level.push(node.left);
            }
        }
        direction ^= 1;
        queue = level;
    }

    return result; //?
}

Level Order Tree Traversal

Ronald — Tue, 12 May 2020 19:28:31 +0000

function levelOrder(root) {

    let queue = [root], result = [];
    function process(node) {
        result.push(node.val);
    }

    while (queue.length) {
        const node = queue.pop();
        process(node);
        if (node.left) queue.unshift(node.left);
        if (node.right) queue.unshift(node.right);
    }

    return result; //?
}