Description:
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:

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

题意：给定一个二维矩阵，模拟Matlab上的reshape函数的功能，将一个二维矩阵的各个维度改变，但是原矩阵中的元素保留不变;

解法：要想转换维度合法，首要的一点就是原数组的行数与列数的乘积与转换后的行数与列数的乘积应当是相等的;满足这一点后，我们只需要将原矩阵的元素按照行优先的顺序依次放入要转换后的数组中就得到转换维度的矩阵了;

class Solution {
    public int[][] matrixReshape(int[][] nums, int r, int c) {
        if (nums.length * nums[0].length != r * c) {
            return nums;
        } //unreasonable number of rows and columns
        int[][] result = new int[r][c];
        int nums_r = 0;
        int nums_c = 0;
        for(int i=0; i<r; i++) {
            for(int j=0; j<c; j++) {
                result[i][j] = nums[nums_r][nums_c];
                if (nums_c + 1 == nums[nums_r].length) {
                    nums_r++;
                    nums_c = 0;
                } else {
                    nums_c++;
                }
            }
        }
        return