leetcode 2022. Convert 1D Array Into 2D Array(python)

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描述

You are given a 0-indexed 1-dimensional (1D) integer array original, and two integers, m and n. You are tasked with creating a 2-dimensional (2D) array with m rows and n columns using all the elements from original.

The elements from indices 0 to n - 1 (inclusive) of original should form the first row of the constructed 2D array, the elements from indices n to 2 * n - 1 (inclusive) should form the second row of the constructed 2D array, and so on.

Return an m x n 2D array constructed according to the above procedure, or an empty 2D array if it is impossible.

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.
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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.
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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.
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Example 4:

Input: original = [3], m = 1, n = 2
Output: []
Explanation:
There is 1 element in original.
It is impossible to make 1 element fill all the spots in a 1x2 2D array, so return an empty 2D array.
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Note:

1 <= original.length <= 5 * 10^4
1 <= original[i] <= 10^5
1 <= m, n <= 4 * 104^
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解析

根据题意,就是给出了一个从 0 开始索引的一维列表 original ,并且有两个整数 m 和 n ,我们的任务就是创建一个 m 行 n 列的二维列表,值都是用的 original 中的值,原始索引 0 到 n - 1(含)的元素应构成构造的二维数组的第一行,索引 n 到 2 * n - 1(含)的元素应构成构造的二维数组的第二行, 以此类推等等。

返回一个按照上述过程构造的 m x n 二维数组,如果不可能,则返回一个空的二维数组。

题干这么长,其实很简单,就是个纸老虎,一个能打的都没有!思路:

  • 先判断 m*n 如果和 original 长度不相等,直接返回空列表
  • 否则初始化一个 result ,然后从左到右每次截取 n 个 original 中的元素加到 result 后面
  • 遍历结束,返回 result

解答

class Solution(object):
    def construct2DArray(self, original, m, n):
        """
        :type original: List[int]
        :type m: int
        :type n: int
        :rtype: List[List[int]]
        """
        if m*n!=len(original) : return []
        result = []
        for i in range(m):
            result.append(original[i*n:(i+1)*n])
        return result   
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运行结果

Runtime: 884 ms, faster than 89.55% of Python online submissions for Convert 1D Array Into 2D Array.
Memory Usage: 22 MB, less than 50.87% of Python online submissions for Convert 1D Array Into 2D Array.
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原题链接:leetcode.com/problems/co…

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