Reshape Matrix

Problem

Given a matrix mat of size m x n and two integers r and c, reshape the matrix into a new one with r rows and c columns. If the reshaping operation cannot be done, return the original matrix.

You should fill the new matrix row by row with the elements from the original matrix in the same row-traversing order.

Examples

matrixReshape([[5,6],[7,8]], 1, 4)
// returns [[5,6,7,8]]
// The original matrix is reshaped to a 1x4 matrix.
// The elements are filled in row-traversing order.

matrixReshape([[5,6],[7,8]], 3, 2)
// returns [[5,6],[7,8]]
// It's impossible to reshape the matrix to a 3x2 matrix
// so the original matrix is returned.

matrixReshape([[9,10],[11,12]], 2, 2)
// returns [[9,10],[11,12]]
// The request does not change the dimensions
// so the original matrix is returned.