Reshape the Matrix

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 needs to be filled with all the elements of the original matrix in the same row-traversing order as they were.

Example 1:

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

Approach

Java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ReshapeMatrix {
    public static void main(String[] args) {
        int mat[][] = { { 1, 2 }, { 3, 4 } };
        int r = 4, c = 1;
        mat = matrixReshape(mat, r, c);
        for (int i = 0; i < mat.length; i++) {
            System.out.println(Arrays.toString(mat[i]));
        }
    }

    // resaphe the matrix into the new
    // dimensions
    static int[][] matrixReshape(int[][] nums, int r, int c) {

        int n = nums.length;
        int m = nums[0].length;
        // if new dimensions are not match
        // then return the original matrix
        if (n * m != r * c)
            return nums;
        else {
            int[][] v = new int[r][c];
            List<Integer> p = new ArrayList<Integer>();

            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    p.add(nums[i][j]);
                }
            }
            int j = 0;
            int cnt = 0;
            int k = 0;
            for (int i = 0; i < p.size(); i++) {
                v[j][k] = p.get(i);
                k++;
                cnt++;
                if (cnt == c) {
                    cnt = 0;
                    k = 0;
                    j++;
                }
            }
            return v;
        }

    }
}

C++

#include <bits/stdc++.h>
using namespace std;

//resaphe the matrix into the new 
//dimensions
vector<vector<int>> matrixReshape(vector<vector<int>>& nums, 
   int r, int c)
{
       vector<vector<int>> v;
      int n=nums.size();
        int m=nums[0].size();
        //if new dimensions are not match 
        //then return the original matrix
        if(n*m!=r*c)
              return nums;
        else
        {
             vector<int> p;
            for(int i=0;i<n;i++)
            {
                for(int j=0;j<m;j++)
                {
                    p.push_back(nums[i][j]);
                }
            }
            vector<int> x;
            for(int i=0;i<p.size();i++)
            {
                x.push_back(p[i]);
                if(x.size()==c)
                {
                    v.push_back(x);
                    x.clear();
                }
            }
             return v;
        }
       
}
int main()
{
    vector<vector<int>> nums = {{1,2},
                               {3,4}};
    int r = 1, c = 4;

    vector<vector<int>> res=matrixReshape(nums,r,c);
    cout<<"[";
    for(int i=0;i<r;i++)
      {
          cout<<"[";
         for(int j=0;j<c;j++)
           {
               if(j!=c-1)
                  cout<<res[i][j]<<",";
               else
                  cout<<res[i][j];
               
           }
         if(i!=r-1)
            cout<<"],";
         else
           cout<<"]";
      }
     cout<<"]";
}