101. 对称二叉树【简单题】

题目链接

// 升级一下initTree的代码
const initTree = (inputList) => {
    const total = inputList.length;
    if(!inputList[0])return null;
    inputList[0] = new TreeNode(inputList[0]);
    inputList.forEach((el,index) => {
        let leftP = null;
        let rightP = null;
        if (!el) return;
        if (index*2+1 < total) {
            leftP = inputList[index*2+1]? new TreeNode(inputList[index*2+1]): null;
            inputList[index*2+1] = leftP;
        } 
        if (index*2+2 < total) {
            rightP = inputList[index*2+2]? new TreeNode(inputList[index*2+2]): null;
            inputList[index*2+2] = rightP;
        }
        inputList[index].left = leftP;
        inputList[index].right = rightP;
    });
    return inputList[0];
  }

function TreeNode(val, left, right) {
    this.val = (val===undefined ? 0 : val)
    this.left = (left===undefined ? null : left)
    this.right = (right===undefined ? null : right)
}

const compare = (left, right) => {
    if (!left && !right) return true;
    else if (!left || !right) return false;
    else if (left && right && left.val !== right.val) return false;
    else {
        // left && right && left.val === right.val
        const outsideRes = compare(left.left, right.right);
        const insideRes = compare(left.right, right.left);
        return outsideRes && insideRes;
    }
}

/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isSymmetric = function(root) {
    return compare(root.left, root.right);
};


// 验证代码
(()=>{
    const input = [1,2,2,3,4,4,3];
    const root = initTree(input);
    console.log('root', root);
    const res = isSymmetric(root);
    console.log('res', res);
  })();