2625. 扁平化嵌套数组
2625. 扁平化嵌套数组
题目
Given a multi-dimensional array arr
and a depth n
, return a flattened version of that array.
A multi-dimensional array is a recursive data structure that contains integers or other multi-dimensional arrays.
A flattened array is a version of that array with some or all of the sub- arrays removed and replaced with the actual elements in that sub-array. This flattening operation should only be done if the current depth of nesting is less than n
. The depth of the elements in the first array are considered to be 0
.
Please solve it without the built-in Array.flat
method.
Example 1:
Input
arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
n = 0
Output
[1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
Explanation
Passing a depth of n=0 will always result in the original array. This is because the smallest possible depth of a subarray (0) is not less than n=0. Thus, no subarray should be flattened.
Example 2:
Input
arr = [1, 2, 3, [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
n = 1
Output
[1, 2, 3, 4, 5, 6, 7, 8, [9, 10, 11], 12, 13, 14, 15]
Explanation
The subarrays starting with 4, 7, and 13 are all flattened. This is because their depth of 0 is less than 1. However [9, 10, 11] remains unflattened because its depth is 1.
Example 3:
Input
arr = [[1, 2, 3], [4, 5, 6], [7, 8, [9, 10, 11], 12], [13, 14, 15]]
n = 2
Output
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
Explanation
The maximum depth of any subarray is 1. Thus, all of them are flattened.
Constraints:
0 <= count of numbers in arr <= 10^5
0 <= count of subarrays in arr <= 10^5
maxDepth <= 1000
-1000 <= each number <= 1000
0 <= n <= 1000
题目大意
请你编写一个函数,它接收一个 多维数组 arr
和它的深度 n
,并返回该数组的 扁平化 后的结果。
多维数组 是一种包含整数或其他多维数组的递归数据结构。
数组 扁平化 是对数组的一种操作,定义是将原数组部分或全部子数组删除,并替换为该子数组中的实际元素。只有当嵌套的数组深度大于 n
时,才应该执行扁平化操作。第一层数组中元素的深度被认为是 0。
请在没有使用内置方法 Array.flat
的前提下解决这个问题。
提示:
0 <= arr 的元素个数 <= 10^5
0 <= arr 的子数组个数 <= 10^5
maxDepth <= 1000
-1000 <= each number <= 1000
0 <= n <= 1000
解题思路
- 定义一个空数组
result
用于存储结果。 - 定义内部递归函数
flattenArray
,使用forEach
遍历输入的嵌套数组。 - 对于数组中的每个元素,:
- 如果是其类型是数组且扁平化深度大于 0,递归调用
flattenArray
函数处理该数组。 - 否则,直接将其添加到结果数组中。
- 如果是其类型是数组且扁平化深度大于 0,递归调用
- 最后返回展平后的结果数组。
复杂度分析
- 时间复杂度:
O(n)
,其中n
是数组中所有元素的总数,每个元素都需要被访问一次。 - 空间复杂度:
O(n)
,用于存储结果数组。
代码
/**
* @param {Array} arr
* @param {number} depth
* @return {Array}
*/
var flat = function (arr, n) {
let res = [];
const flattenArray = (arr, n) => {
arr.forEach((item) => {
if (Array.isArray(item) && n > 0) {
// 递归调用
flattenArray(item, n - 1);
} else {
// 添加非数组元素
res.push(item);
}
});
};
flattenArray(arr, n);
return res;
};
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