題目敘述 Convert 1D Array Into 2D Array
給定一個一維輸入陣列，請轉換成高度為m*寬度為n的二維陣列，
以二維陣列的形式輸出。
示意圖
測試範例
Example 1:
Input: original = [1,2,3,4], m = 2, n = 2
Output: [[1,2],[3,4]]
Explanation: The constructed 2D array should contain 2 rows and 2 columns.
The first group of n=2 elements in original, [1,2], becomes the first row in the constructed 2D array.
The second group of n=2 elements in original, [3,4], becomes the second row in the constructed 2D array.
Example 2:
Input: original = [1,2,3], m = 1, n = 3
Output: [[1,2,3]]
Explanation: The constructed 2D array should contain 1 row and 3 columns.
Put all three elements in original into the first row of the constructed 2D array.
Example 3:
Input: original = [1,2], m = 1, n = 1
Output: []
Explanation: There are 2 elements in original.
It is impossible to fit 2 elements in a 1x1 2D array, so return an empty 2D array.
約束條件
Constraints:
1 <= original.length <= 5 * 10^4
輸入陣列的高度介於1~五萬之間。
1 <= original[i] <= 105
輸入陣列的寬度介於1~五萬之間。
1 <= m, n <= 4 * 10^4
二維陣列的高和寬都介於1~四萬之間。
演算法 List comprehension
根據指定的高度和寬度，計算是否可以相容轉換?
如果不行，直接輸出空陣列[]。
# total element count of input array
element_count = len(original)
if element_count != m * n:
# Reject if element count mismatch with new 2D array
return []
如果可以，根據列表推導式直接轉換成對應的二維陣列即可。
程式碼 List comprehension
class Solution:
def construct2DArray(self, original: List[int], m: int, n: int) -> List[List[int]]:
# total element count of input array
element_count = len(original)
if element_count != m * n:
# Reject if element count mismatch with new 2D array
return []
# reshape to specified 2D array by list comprehension
return [ original[y*n:y*n+n] for y in range(m)]
複雜度分析
時間複雜度: O(m*n)
每個陣列元素搬移一次，總共m*n個元素。
空間複雜度: O(m*n)
每個陣列元素需要一個新的空間，總共m*n個元素。
