[LeetCode] 566. Reshape the Matrix

轉自LeetCode

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.

<Solution>

想法如下

• 先檢查 reshape 後的 matrix 所包含的元素個數，是否和原本的一樣，不是就回傳原本的 matrix

• 如果個數一樣，那就將元素一個一個放到新的 matrix 中

code 如下

C++(作法一：去檢查原本 matrix 的邊界)

Java(作法二：2D array 在記憶體中也是 1D 的存放方式，row index = 計數/col, col index = 計數 % col。參考解答)