题目描述：

LeetCode 566. Reshape the Matrix

In MATLAB, there is a very useful function called 'reshape', which can reshape a matrix into a new one with different size but keep its original data.

You're given a matrix represented by a two-dimensional array, and two positive integers r and c representing the row number and column number of the wanted reshaped matrix, respectively.

The reshaped matrix need to be filled with all the elements of the original matrix in the same row-traversing order as they were.

If the 'reshape' operation with given parameters is possible and legal, output the new reshaped matrix; Otherwise, output the original matrix.

Example 1:

Input: 
nums = 
[[1,2],
 [3,4]]
r = 1, c = 4
Output: 
[[1,2,3,4]]
Explanation:
The row-traversing of nums is [1,2,3,4]. The new reshaped matrix is a 1 * 4 matrix, fill it row by row by using the previous list.

Example 2:

Input: 
nums = 
[[1,2],
 [3,4]]
r = 2, c = 4
Output: 
[[1,2],
 [3,4]]
Explanation:
There is no way to reshape a 2 * 2 matrix to a 2 * 4 matrix. So output the original matrix.

Note:

1. The height and width of the given matrix is in range [1, 100].
2. The given r and c are all positive.

题目大意：

给定二维矩阵nums，将其转化为r行c列的新矩阵。若无法完成转化，返回原矩阵。

注意：

1. 给定矩阵的高度和宽度范围[1, 100]
2. r和c都是正数

解题思路：

模拟题，详见代码

Python代码：

class Solution(object):
    def matrixReshape(self, nums, r, c):
        """
        :type nums: List[List[int]]
        :type r: int
        :type c: int
        :rtype: List[List[int]]
        """
        h, w = len(nums), len(nums[0])
        if h * w != r * c: return nums
        ans = []
        for x in range(r):
            row = []
            for y in range(c):
                row.append(nums[(x * c + y) / w][(x * c + y) % w])
            ans.append(row)
        return ans

比赛时编写的代码如下

Python代码：

class Solution(object):
    def matrixReshape(self, nums, r, c):
        """
        :type nums: List[List[int]]
        :type r: int
        :type c: int
        :rtype: List[List[int]]
        """
        h, w = len(nums), len(nums[0])
        if h * w != r * c: return nums
        ans = []
        p = q = 0
        for x in range(r):
            row = []
            for y in range(c):
                row.append(nums[p][q])
                q += 1
                if q == w:
                    p += 1
                    q = 0
            ans.append(row)
        return ans

 

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