I'm doing a program on the addition of 2 Sparse Matrices. This is what I have coded-
import java.io.*;
class Sparse
{
int r,c,m[][],s[][],count,rt;
static int res[][];
public Sparse()
{
count=0;
rt=1;
}
//Take the matrix
public void read() throws Throwable
{
BufferedReader buff=new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter the number of rows: ");
r=Integer.parseInt(buff.readLine());
System.out.print("Enter the number of columns: ");
c=Integer.parseInt(buff.readLine());
m=new int[r][c];
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
System.out.print("Enter the element m[" + i +"]["+ j + "]: ");
m[i][j]=Integer.parseInt(buff.readLine());
if(m[i][j] !=0)
count++;
}
}
}
public void display() throws Throwable
{
System.out.println("The matrix is as follows: ");
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
System.out.print(m[i][j]+" ");
}
System.out.println();
}
}
public void displaysparse() throws Throwable
{
System.out.println("The sparse matrix is as follows: ");
for(int i=0;i<rt;i++)
{
for(int j=0;j<3;j++)
{
System.out.print(s[i][j]+" ");
}
System.out.println();
}
}
//Create the sparse
public void create()
{
s=new int[count+1][3];
s[0][0]=r;
s[0][1]=c;
s[0][2]=count;
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
if (m[i][j]!=0)
{
s[rt][0]=i;
s[rt][1]=j;
s[rt][2]=m[i][j];
rt++;
}
}
}
}
public static void add(Sparse a,Sparse b) throws Throwable
{
int temp_count=0;
if (a.r== b.r && a.c==b.c)
{
for(int i=1;i<a.rt;i++)
{
//Getting a row of s[i][j] belonging to 'a'
for(int j=1;j<b.rt;j++)
{
if(a.s[i][0]==b.s[j][0] && a.s[i][1]==b.s[j][1])
temp_count++;
}
}
//System.out.println("Common Elements: "+temp_count);
res=new int[a.count+b.count-temp_count+1][3];
res[0][0]=a.r;
res[0][1]=a.c;
res[0][2]=a.count+b.count-temp_count;
int x=1;
boolean flag;
for(int i=1;i<a.rt;i++)
{
flag=false;
//Getting a row of s[i][j] belonging to 'a'
for(int j=1;j<b.rt;j++)
{
if(a.s[i][0]==b.s[j][0] && a.s[i][1]==b.s[j][1])
{
res[x][0]=a.s[i][0];
res[x][1]=a.s[i][1];
res[x][2]=a.s[i][2]+b.s[j][2];
x++;
flag=true;
}
}
if(flag==false)
{
//this element of 'a' does not find a match in 'b', just put it in res
res[x][0]=a.s[i][0];
res[x][1]=a.s[i][1];
res[x][2]=a.s[i][2];
x++;
}
}
int x2;
x2=x;
//add the remaining elements of 'b'
for(int i=1;i<b.rt;i++)
{
flag=false;
//Getting a row of s[i][j] belonging to 'b'
for(int j=1;j<x2;j++)
{
if(b.s[i][0]==res[j][0] && b.s[i][1]==res[j][1])
{
flag=true;
}
}
if(flag==false)
{
//this element of 'b' does not find a match in res, just append in res
res[x][0]=b.s[i][0];
res[x][1]=b.s[i][1];
res[x][2]=b.s[i][2];
x++;
}
}
//Display RES
System.out.println("The sum of the matrices is: ");
for(int i=0;i<x;i++)
{
for(int j=0;j<3;j++)
{
System.out.print(res[i][j]+" ");
}
System.out.println();
}
}
else
{
System.out.println("The matrices cannot be added as their dimensions do not match");
System.exit(1);
}
}
}
class SpMx
{
public static void main(String[] args) throws Throwable
{
Sparse a=new Sparse();
Sparse b=new Sparse();
System.out.println("Entering the first matrix: ");
a.read();
a.display();
a.create();
a.displaysparse();
System.out.println("Entering the second matrix: ");
b.read();
b.display();
b.create();
b.displaysparse();
Sparse.add(a,b);
}
}As you can see from the code, the sum of a & b is held in res.
I had to go through a loop to count the number of elements that would appear in the 'res' array.
Instead of this, if I create 'res' as an ArrayList, how can I get back a 2D array from it?
