main.go

// Source: https://leetcode.com/problems/reshape-the-matrix
// Title: Reshape the Matrix
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// In MATLAB, there is a handy function called reshape which can reshape an m x n matrix into a new one with a different size r x c keeping its original data.
//
// 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.
//
// Example 1:
//
//   https://assets.leetcode.com/uploads/2021/04/24/reshape1-grid.jpg
//
//   Input: mat = [[1,2],[3,4]], r = 1, c = 4
//   Output: [[1,2,3,4]]
//
// Example 2:
//
//   https://assets.leetcode.com/uploads/2021/04/24/reshape2-grid.jpg
//
//   Input: mat = [[1,2],[3,4]], r = 2, c = 4
//   Output: [[1,2],[3,4]]
//
// Constraints:
//
//   m == mat.length
//   n == mat[i].length
//   1 <= m, n <= 100
//   -1000 <= mat[i][j] <= 1000
//   1 <= r, c <= 300
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

func matrixReshape(mat [][]int, r int, c int) [][]int {
	m := len(mat)
	n := len(mat[0])

	if (m == r && n == c) || (m*n != r*c) {
		return mat
	}

	res := make([][]int, r)
	for i := 0; i < r; i++ {
		res[i] = make([]int, c)
	}

	for k := 0; k < m*n; k++ {
		res[k/c][k%c] = mat[k/n][k%n]
	}

	return res
}