LeetCode - Easy - 566. Reshape the Matrix

左手的ㄟ右手 2022-10-15 00:43 147阅读 0赞

## Topic ##

*  Array

## Description ##

[https://leetcode.com/problems/reshape-the-matrix/][https_leetcode.com_problems_reshape-the-matrix]

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 row number and column number 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:**

![743f3e7abedbf0ee412d2280540b334c.png][]

Input: mat = [[1,2],[3,4]], r = 1, c = 4
    Output: [[1,2,3,4]]

**Example 2:**

![7019730ed105dbf6ed0bf55b59843995.png][]

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

## Analysis ##

略

## Submission ##

public class ReshapeTheMatrix { 
        public int[][] matrixReshape(int[][] mat, int r, int c) { 
            if(mat.length * mat[0].length != r * c)
            	return mat;
        	
            int[][] result = new int[r][c]; 
        	int rp = 0, cp = 0;
            
            for(int[] array : mat) 
            	for(int i : array) { 
            		result[rp][cp++] = i;
            		if(cp == c) { 
            			rp++;
            			cp = 0;
            		}
            	}
            
        	return result;
        }
    }

## Test ##

import static org.junit.Assert.*;
    import org.junit.Test;
    
    public class ReshapeTheMatrixTest { 
    
    	@Test
    	public void test() { 
    		ReshapeTheMatrix obj = new ReshapeTheMatrix();
    
    		int[][] result1 = obj.matrixReshape(new int[][] { { 1, 2}, { 3, 4}}, 1, 4);
    		int[][] expected1 = { { 1, 2, 3, 4}};
    		for(int i = 0; i < expected1.length; i++) 
    			assertArrayEquals(expected1[i], result1[i]);
    
    		
    		int[][] result2 = obj.matrixReshape(new int[][] { { 1, 2}, { 3, 4}}, 2, 4);
    		int[][] expected2 = { { 1, 2}, { 3, 4}};
    		for(int i = 0; i < expected2.length; i++)
    			assertArrayEquals(expected2[i], result2[i]);
    		
    	}
    }

[https_leetcode.com_problems_reshape-the-matrix]: https://leetcode.com/problems/reshape-the-matrix/
[743f3e7abedbf0ee412d2280540b334c.png]: /images/20221014/c7f8b0ed99484a9091339b79afb50368.png
[7019730ed105dbf6ed0bf55b59843995.png]: /images/20221014/286e23ca40d7434ab9e451e52f2d0896.png