You are given an `m x n` matrix `mat` and two integers `r` and `c` representing the number of rows and the number of columns of the wanted reshaped matrix. The reshaped matrix should be filled with all the elements of the original matrix in the same row-traversing order as they were.
``package questionsimport _utils.UseCommentAsDocumentationimport utils.shouldBe/** * You are given an `m x n` matrix `mat` and two integers `r` and `c` * representing the number of rows and the number of columns of the wanted reshaped matrix. * The reshaped matrix should 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. * * [Source](https://leetcode.com/problems/reshape-the-matrix/) */@UseCommentAsDocumentationprivate fun matrixReshape(mat: Array<IntArray>, r: Int, c: Int): Array<IntArray> {    val col = mat.size    val row = mat.size    if (r * c != col * row) {        return mat    }    val result = Array<IntArray>(r) { IntArray(c) { -1 } }    var rowIndex = 0    var colIndex = 0    for (i in 0 until row) {        for (j in 0 until col) {            if (colIndex >= c) {                rowIndex++                colIndex = 0            }            result[rowIndex][colIndex] = mat[i][j]            colIndex++        }    }    return result}fun main() {    run() {        val result = matrixReshape(mat = arrayOf(intArrayOf(1, 2), intArrayOf(3, 4)), r = 1, c = 4)        val expected = arrayOf(intArrayOf(1, 2, 3, 4))        result.forEachIndexed { index, ints ->            ints shouldBe expected[index]        }    }    run {        val result = matrixReshape(            mat = arrayOf(                intArrayOf(1, 2),                intArrayOf(3, 4)            ), r = 2, c = 4        )        val expected = arrayOf(            intArrayOf(1, 2),            intArrayOf(3, 4)        )        result.forEachIndexed { index, ints ->            ints shouldBe expected[index]        }    }}``