A matrix is a two-dimensional data object made of m rows and n columns, therefore having total m x n values. If most of the elements of the matrix have 0 value, then it is called a sparse matrix.
Why to use Sparse Matrix instead of simple matrix ?
- Storage: There are lesser non-zero elements than zeros and thus lesser memory can be used to store only those elements.
- Computing time: Computing time can be saved by logically designing a data structure traversing only non-zero elements..
Example:
0 0 3 0 4
0 0 5 7 0
0 0 0 0 0
0 2 6 0 0
Representing a sparse matrix by a 2D array leads to wastage of lots of memory as zeroes in the matrix are of no use in most of the cases. So, instead of storing zeroes with non-zero elements, we only store non-zero elements. This means storing non-zero elements with triples- (Row, Column, value).
Sparse Matrix Representations can be done in many ways following are two common representations:
- Array representation
- Linked list representation
Method 1: Using Arrays:
2D array is used to represent a sparse matrix in which there are three rows named as
- Row: Index of row, where non-zero element is located
- Column: Index of column, where non-zero element is located
- Value: Value of the non zero element located at index – (row,column)
Implementation:
C++
#include <iostream>
using namespace std;
int main()
{
int sparseMatrix[4][5] =
{
{0 , 0 , 3 , 0 , 4 },
{0 , 0 , 5 , 7 , 0 },
{0 , 0 , 0 , 0 , 0 },
{0 , 2 , 6 , 0 , 0 }
};
int size = 0;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
size++;
int compactMatrix[3][size];
int k = 0;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
{
compactMatrix[0][k] = i;
compactMatrix[1][k] = j;
compactMatrix[2][k] = sparseMatrix[i][j];
k++;
}
for (int i=0; i<3; i++)
{
for (int j=0; j<size; j++)
cout <<" "<< compactMatrix[i][j];
cout <<"\n";
}
return 0;
}
|
C
#include<stdio.h>
int main()
{
int sparseMatrix[4][5] =
{
{0 , 0 , 3 , 0 , 4 },
{0 , 0 , 5 , 7 , 0 },
{0 , 0 , 0 , 0 , 0 },
{0 , 2 , 6 , 0 , 0 }
};
int size = 0;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
size++;
int compactMatrix[3][size];
int k = 0;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
{
compactMatrix[0][k] = i;
compactMatrix[1][k] = j;
compactMatrix[2][k] = sparseMatrix[i][j];
k++;
}
for (int i=0; i<3; i++)
{
for (int j=0; j<size; j++)
printf("%d ", compactMatrix[i][j]);
printf("\n");
}
return 0;
}
|
Java
class GFG
{
public static void main(String[] args)
{
int sparseMatrix[][]
= {
{0, 0, 3, 0, 4},
{0, 0, 5, 7, 0},
{0, 0, 0, 0, 0},
{0, 2, 6, 0, 0}
};
int size = 0;
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 5; j++)
{
if (sparseMatrix[i][j] != 0)
{
size++;
}
}
}
int compactMatrix[][] = new int[3][size];
int k = 0;
for (int i = 0; i < 4; i++)
{
for (int j = 0; j < 5; j++)
{
if (sparseMatrix[i][j] != 0)
{
compactMatrix[0][k] = i;
compactMatrix[1][k] = j;
compactMatrix[2][k] = sparseMatrix[i][j];
k++;
}
}
}
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < size; j++)
{
System.out.printf("%d ", compactMatrix[i][j]);
}
System.out.printf("\n");
}
}
}
|
Python3
sparseMatrix = [[0,0,3,0,4],[0,0,5,7,0],[0,0,0,0,0],[0,2,6,0,0]]
size = 0
for i in range(4):
for j in range(5):
if (sparseMatrix[i][j] != 0):
size += 1
rows, cols = (3, size)
compactMatrix = [[0 for i in range(cols)] for j in range(rows)]
k = 0
for i in range(4):
for j in range(5):
if (sparseMatrix[i][j] != 0):
compactMatrix[0][k] = i
compactMatrix[1][k] = j
compactMatrix[2][k] = sparseMatrix[i][j]
k += 1
for i in compactMatrix:
print(i)
|
C#
using System;
class Program {
static void Main(string[] args)
{
int[, ] sparseMatrix
= new int[4, 5] { { 0, 0, 3, 0, 4 },
{ 0, 0, 5, 7, 0 },
{ 0, 0, 0, 0, 0 },
{ 0, 2, 6, 0, 0 } };
int size = 0;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatrix[i, j] != 0)
size++;
int[, ] compactMatrix = new int[3, size];
int k = 0;
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 5; j++)
if (sparseMatrix[i, j] != 0) {
compactMatrix[0, k] = i;
compactMatrix[1, k] = j;
compactMatrix[2, k]
= sparseMatrix[i, j];
k++;
}
}
for (int i = 0; i < 3; i++) {
for (int j = 0; j < size; j++)
Console.Write(" " + compactMatrix[i, j]);
Console.WriteLine();
}
}
}
|
Javascript
let sparseMatrix =
[
[0 , 0 , 3 , 0 , 4 ],
[0 , 0 , 5 , 7 , 0 ],
[0 , 0 , 0 , 0 , 0 ],
[0 , 2 , 6 , 0 , 0 ]
];
let size = 0;
for (let i = 0; i < 4; i++)
for (let j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
size++;
let compactMatrix = new Array(3);
for (var i = 0; i < 3; i++)
compactMatrix[i] = new Array(size);
let k = 0;
for (let i = 0; i < 4; i++)
for (let j = 0; j < 5; j++)
if (sparseMatrix[i][j] != 0)
{
compactMatrix[0][k] = i;
compactMatrix[1][k] = j;
compactMatrix[2][k] = sparseMatrix[i][j];
k++;
}
for (let i=0; i<3; i++)
{
for (let j=0; j<size; j++)
process.stdout.write(" " + compactMatrix[i][j]);
console.log()
}
|
Output 0 0 1 1 3 3
2 4 2 3 1 2
3 4 5 7 2 6
Time Complexity: O(NM), where N is the number of rows in the sparse matrix, and M is the number of columns in the sparse matrix.
Auxiliary Space: O(NM), where N is the number of rows in the sparse matrix, and M is the number of columns in the sparse matrix.
Method 2: Using Linked Lists
In linked list, each node has four fields. These four fields are defined as:
- Row: Index of row, where non-zero element is located
- Column: Index of column, where non-zero element is located
- Value: Value of the non zero element located at index – (row,column)
- Next node: Address of the next node
C++
#include<iostream>
using namespace std;
class Node
{
public:
int row;
int col;
int data;
Node *next;
};
void create_new_node(Node **p, int row_index,
int col_index, int x)
{
Node *temp = *p;
Node *r;
if (temp == NULL)
{
temp = new Node();
temp->row = row_index;
temp->col = col_index;
temp->data = x;
temp->next = NULL;
*p = temp;
}
else
{
while (temp->next != NULL)
temp = temp->next;
r = new Node();
r->row = row_index;
r->col = col_index;
r->data = x;
r->next = NULL;
temp->next = r;
}
}
void printList(Node *start)
{
Node *ptr = start;
cout << "row_position:";
while (ptr != NULL)
{
cout << ptr->row << " ";
ptr = ptr->next;
}
cout << endl;
cout << "column_position:";
ptr = start;
while (ptr != NULL)
{
cout << ptr->col << " ";
ptr = ptr->next;
}
cout << endl;
cout << "Value:";
ptr = start;
while (ptr != NULL)
{
cout << ptr->data << " ";
ptr = ptr->next;
}
}
int main()
{
int sparseMatrix[4][5] = { { 0 , 0 , 3 , 0 , 4 },
{ 0 , 0 , 5 , 7 , 0 },
{ 0 , 0 , 0 , 0 , 0 },
{ 0 , 2 , 6 , 0 , 0 } };
Node *first = NULL;
for(int i = 0; i < 4; i++)
{
for(int j = 0; j < 5; j++)
{
if (sparseMatrix[i][j] != 0)
create_new_node(&first, i, j,
sparseMatrix[i][j]);
}
}
printList(first);
return 0;
}
|
C
#include<stdio.h>
#include<stdlib.h>
struct Node
{
int value;
int row_position;
int column_postion;
struct Node *next;
};
void create_new_node(struct Node** start, int non_zero_element,
int row_index, int column_index )
{
struct Node *temp, *r;
temp = *start;
if (temp == NULL)
{
temp = (struct Node *) malloc (sizeof(struct Node));
temp->value = non_zero_element;
temp->row_position = row_index;
temp->column_postion = column_index;
temp->next = NULL;
*start = temp;
}
else
{
while (temp->next != NULL)
temp = temp->next;
r = (struct Node *) malloc (sizeof(struct Node));
r->value = non_zero_element;
r->row_position = row_index;
r->column_postion = column_index;
r->next = NULL;
temp->next = r;
}
}
void PrintList(struct Node* start)
{
struct Node *temp, *r, *s;
temp = r = s = start;
printf("row_position: ");
while(temp != NULL)
{
printf("%d ", temp->row_position);
temp = temp->next;
}
printf("\n");
printf("column_postion: ");
while(r != NULL)
{
printf("%d ", r->column_postion);
r = r->next;
}
printf("\n");
printf("Value: ");
while(s != NULL)
{
printf("%d ", s->value);
s = s->next;
}
printf("\n");
}
int main()
{
int sparseMatric[4][5] =
{
{0 , 0 , 3 , 0 , 4 },
{0 , 0 , 5 , 7 , 0 },
{0 , 0 , 0 , 0 , 0 },
{0 , 2 , 6 , 0 , 0 }
};
struct Node* start = NULL;
for (int i = 0; i < 4; i++)
for (int j = 0; j < 5; j++)
if (sparseMatric[i][j] != 0)
create_new_node(&start, sparseMatric[i][j], i, j);
PrintList(start);
return 0;
}
|
Java
import java.util.*;
public class SparseMatrix {
static Node first = null;
public static class Node {
int row;
int col;
int data;
Node next;
};
public static void main(String[] args)
{
int[][] sparseMatrix = { { 0, 0, 3, 0, 4 },
{ 0, 0, 5, 7, 0 },
{ 0, 0, 0, 0, 0 },
{ 0, 2, 6, 0, 0 } };
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 5; j++) {
if (sparseMatrix[i][j] != 0) {
create_new_node(i, j,
sparseMatrix[i][j]);
}
}
}
printList(first);
}
private static void
create_new_node(int row_index, int col_index, int x)
{
Node temp = first;
Node r;
if (temp == null) {
temp = new Node();
temp.row = row_index;
temp.col = col_index;
temp.data = x;
temp.next = null;
first = temp;
}
else {
while (temp.next != null)
temp = temp.next;
r = new Node();
r.row = row_index;
r.col = col_index;
r.data = x;
r.next = null;
temp.next = r;
}
}
public static void printList(Node start)
{
Node ptr = start;
System.out.print("row_position:");
while (ptr != null) {
System.out.print(ptr.row + " ");
ptr = ptr.next;
}
System.out.println("");
System.out.print("column_position:");
ptr = start;
while (ptr != null) {
System.out.print(ptr.col + " ");
ptr = ptr.next;
}
System.out.println("");
System.out.print("Value:");
ptr = start;
while (ptr != null) {
System.out.print(ptr.data + " ");
ptr = ptr.next;
}
}
}
|
Python3
class Node:
__slots__ = "row", "col", "data", "next"
def __init__(self, row=0, col=0, data=0, next=None):
self.row = row
self.col = col
self.data = data
self.next = next
class Sparse:
def __init__(self):
self.head = None
self.temp = None
self.size = 0
def __len__(self):
return self.size
def isempty(self):
return self.size == 0
def create_new_node(self, row, col, data):
newNode = Node(row, col, data, None)
if self.isempty():
self.head = newNode
else:
self.temp.next = newNode
self.temp = newNode
self.size += 1
def PrintList(self):
temp = r = s = self.head
print("row_position:", end=" ")
while temp != None:
print(temp.row, end=" ")
temp = temp.next
print()
print("column_postion:", end=" ")
while r != None:
print(r.col, end=" ")
r = r.next
print()
print("Value:", end=" ")
while s != None:
print(s.data, end=" ")
s = s.next
print()
if __name__ == "__main__":
s = Sparse()
sparseMatric = [[0, 0, 3, 0, 4],
[0, 0, 5, 7, 0],
[0, 0, 0, 0, 0],
[0, 2, 6, 0, 0]]
for i in range(4):
for j in range(5):
if sparseMatric[i][j] != 0:
s.create_new_node(i, j, sparseMatric[i][j])
s.PrintList()
|
C#
using System;
class Program
{
static Node first = null;
public class Node {
public int row;
public int col;
public int data;
public Node next;
};
static void Main(string[] args)
{
int[, ] sparseMatrix = { { 0, 0, 3, 0, 4 },
{ 0, 0, 5, 7, 0 },
{ 0, 0, 0, 0, 0 },
{ 0, 2, 6, 0, 0 } };
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 5; j++) {
if (sparseMatrix[i, j] != 0) {
create_new_node(i, j,
sparseMatrix[i, j]);
}
}
}
printList(first);
}
private static void
create_new_node(int row_index, int col_index, int x)
{
Node temp = first;
Node r;
if (temp == null) {
temp = new Node();
temp.row = row_index;
temp.col = col_index;
temp.data = x;
temp.next = null;
first = temp;
}
else
{
while (temp.next != null)
temp = temp.next;
r = new Node();
r.row = row_index;
r.col = col_index;
r.data = x;
r.next = null;
temp.next = r;
}
}
public static void printList(Node start)
{
Node ptr = start;
Console.Write("row_position:");
while (ptr != null) {
Console.Write(ptr.row + " ");
ptr = ptr.next;
}
Console.WriteLine("");
Console.Write("column_position:");
ptr = start;
while (ptr != null) {
Console.Write(ptr.col + " ");
ptr = ptr.next;
}
Console.WriteLine("");
Console.Write("Value:");
ptr = start;
while (ptr != null) {
Console.Write(ptr.data + " ");
ptr = ptr.next;
}
}
}
|
Javascript
class Node
{
constructor(row, col, data)
{
this.row = row;
this.col = col;
this.data = data;
this.next = null;
}
}
class Sparse
{
constructor()
{
this.head = null
this.temp = null
this.size = 0
}
len()
{
return this.size
}
isempty()
{
return this.size == 0
}
create_new_node(row, col, data)
{
let newNode = new Node(row, col, data)
if (this.isempty())
this.head = newNode
else
(this.temp).next = newNode
this.temp = newNode
this.size += 1
}
PrintList()
{
let temp = this.head
let r = this.head
let s = this.head
process.stdout.write("row_position: ")
while (temp != null)
{
process.stdout.write(temp.row + " ")
temp = temp.next
}
console.log()
process.stdout.write("column_postion: ")
while (r != null)
{
process.stdout.write(r.col + " " )
r = r.next
}
console.log()
process.stdout.write("Value: ")
while (s != null)
{
process.stdout.write(s.data + " ")
s = s.next
}
console.log()
}
}
let s = new Sparse()
let sparseMatric = [[0, 0, 3, 0, 4],
[0, 0, 5, 7, 0],
[0, 0, 0, 0, 0],
[0, 2, 6, 0, 0]]
for (var i = 0; i < 4; i++)
for (var j = 0; j < 5; j++)
if (sparseMatric[i][j] != 0)
{
s.create_new_node(i, j, sparseMatric[i][j])
s.data = sparseMatric[i][j]
}
s.PrintList()
|
Outputrow_position:0 0 1 1 3 3
column_position:2 4 2 3 1 2
Value:3 4 5 7 2 6
Time Complexity: O(N*M), where N is the number of rows in the sparse matrix, and M is the number of columns in the sparse matrix.
Auxiliary Space: O(K), where K is the number of non-zero elements in the array.
Other representations:
As a Dictionary where row and column numbers are used as keys and values are matrix entries. This method saves space but sequential access of items is costly.
As a list of list. The idea is to make a list of rows and every item of list contains values. We can keep list items sorted by column numbers.
Sparse Matrix and its representations | Set 2 (Using List of Lists and Dictionary of keys)
This article is contributed by Akash Gupta.If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.