Given an object or an array, return if it is empty.
- An empty object contains no key-value pairs.
- An empty array contains no elements.
You may assume the object or array is the output of JSON.parse.
Example 1:
Input: obj = {"x": 5, "y": 42}
Output: false
Explanation: The object has 2 key-value pairs so it is not empty.
Example 2:
Input: obj = {}
Output: true
Explanation: The object doesn't have any key-value pairs so it is empty.
Example 3:
Input: obj = [null, false, 0] Output: false Explanation: The array has 3 elements so it is not empty.
Constraints:
-
2 <= JSON.stringify(obj).length <= 105
Can you solve it in O(1) time?
方法一：遍历
我们可以遍历对象或数组，如果遍历到了第一个元素，就返回 false，否则返回 true。
时间复杂度
function isEmpty(obj: Record<string, any> | any[]): boolean {
for (const x in obj) {
return false;
}
return true;
}