Published Feb 20, 2022
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Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).
Input: root = [1,2,2,3,4,4,3]
Output: true
Input: root = [1,2,2,null,3,null,3]
Output: false
- The number of nodes in the tree is in the range [1, 1000].
- -100 <= Node.val <= 100
/**
* Definition for a binary tree node.
* class TreeNode {
* val: number
* left: TreeNode | null
* right: TreeNode | null
* constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
* }
*/
function isSymmetric(root: TreeNode | null): boolean {
let queue: TreeNode[] = [];
queue.push(root.left);
queue.push(root.right);
while(queue.length !== 0) {
const LEN: number = queue.length;
for(let i = 0; i < LEN/2; i++){
let front: TreeNode = queue.shift();
let end: TreeNode = queue.pop();
if(front === null && end === null) continue;
if((front === null && end !== null) || (front !== null && end === null) || (front.val !== end.val)) return false;
queue.unshift(front.left);
queue.unshift(front.right);
queue.push(end.right)
queue.push(end.left);
}
}
return true;
};