[110] 平衡二叉树

details

var isBalanced = function (root) {
    if (root == null) return true;
    return Math.abs(maxDepth(root.left) - maxDepth(root.right)) <= 1 && isBalanced(root.left) && isBalanced(root.right);

    function maxDepth(node) {
        if (node == null) return 0;
        let left = maxDepth(node.left);
        let right = maxDepth(node.right);
        return Math.max(left, right) + 1;
    }
};

var isBalanced = function (root) {
    return getHeight(root) !== -1;
};
function getHeight(root) {
    if (root === null) return 0;

    let leftHeight = getHeight(root.left);
    if (leftHeight === -1) return -1; // 左子树不平衡，直接返回

    let rightHeight = getHeight(root.right);
    if (rightHeight === -1) return -1; // 右子树不平衡，直接返回

    if (Math.abs(leftHeight - rightHeight) > 1) return -1; // 当前节点不平衡，返回-1

    return Math.max(leftHeight, rightHeight) + 1; // 返回节点的高度
}