Interview Question Reshape the Matrix

By Fatih KABAKCI

The problem is to create a function that reshapes the matrix to a new form that satisfies the matrix size, in another words, does not violate the rules in terms of matrix laws.

Problem #566 - Reshape the Matrix

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..

Difficulty: Easy

Solution in Java

package com.fatihkabakci.Easy.ReshapeMatrix;

/**
 * @author fkabakci 
 * Problem 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 are 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.

 * Solution:
 * 1. Check the condition that if the intended new matrix applies the rules
 * 	  If so, transfer all the data to the new matrix.
 *    Otherwise, return the same matrix.
 */

public class Solution {
	public int[][] matrixReshape(int[][] nums, int r, int c) {
		int n = nums.length, m = nums[0].length; 
		if(n * m != r * c) return nums;
		
		int [][] matrix = new int[r][c];
		int row = 0, col = 0;
		for(int i = 0; i < n; i++) {
			for(int j = 0; j < m; j++) {
				matrix[row][col] = nums[i][j];
				if(++col == c) {
					col = 0;
					row++;
				}
			}
		}
        return matrix;
    }
}