Two Dimensional Array
It is a collection of data elements of same data type arranged in rows and columns (which is known as two dimensions).
Declaration of Two-Dimensional Array
Type arrayName[numberOfRows][numberOfColumn];
Initialization of Two-Dimensional Array
- An two-dimensional array can be initialized along with declaration.
- For two-dimensional array initialization, elements of each row are enclosed within curly braces and separated by commas.
- All rows are enclosed within curly braces.
int A[4][3] = {{22, 23, 10},
{15, 25, 13},
{20, 74, 67},
{11, 18, 14}};
Referring to Array Elements
- To access the elements of a two-dimensional array, we need a pair of indices: one for the row position and one for the column position. The format is as simple as:
name[rowIndex][columnIndex]
Examples:
cout<<A[1][2]; //print an array element
A[1][2]=13; // assign value to an array element
cin>>A[1][2]; //input element
Using Loop to input an Two-Dimensional Array from user
int mat[3][5], row, col ;
for (row = 0; row < 3; row++)
for (col = 0; col < 5; col++)
cin >> mat[row][col];
Arrays as Parameters
- Two-dimensional arrays can be passed as parameters to a function, and they are passed by reference.
- While defining a two-dimensional array as a formal parameter, we can omit the size of the first dimension but not the second one; that is, the number of columns must be defined.
- For example:
void print(int A[][3],int N, int M)- In order to pass to this function an array declared as:
int arr[4][3];
we need to write a call like this:
print(arr); Here is a complete example:
#include <iostream.h>
#include <conio.h>
void print(int A[][3],int N, int M)
{
for (R = 0; R < N; R++)
for (C = 0; C < M; C++)
cout << A[R][C];
}
int main ()
{
int arr[4][3] ={{12, 29, 11},
{25, 25, 13},
{24, 64, 67},
{11, 18, 14}};
print(arr,4,3);
return 0;
}
Function to read the array A
void Read(int A[][20], int N, int M)
{
for(int R=0;R<N;R++)
for(int C=0;C<M;C++)
{
cout<<"(R<<','<<")?";
cin>>A[R][C];
}
}
Function to display content of a two dimensional array A
void Display(int A[][20],int N, int M)
{
for(int R=0;R<N;R++)
{
for(int C=0;C<M;C++)
cout<<setw(10)<<A[R][C];
cout<<endl;
}
}
Function to find the sum of two dimensional arrays A and B
void Addition(int A[][20], int B[][20],int N, int M)
{
for(int R=0;R<N;R++)
for(int C=0;C<M;C++)
C[R][C]=A[R][C]+B[R][C];
}
Function to multiply two dimensional arrays A and B of order NxL and LxM
void Multiply(int A[][20], int B[][20], int C[][20],int N, int L, int M)
{
for(int R=0;R<N;R++)
for(int C=0;C<M;C++)
{
C[R][C]=0;
for(int T=0;T<L;T++)
C[R][C]+=A[R][T]*B[T][C];
}
}
Function to find & display sum of rows & sum of cols. of a 2 dim. array A
void SumRowCol(int A[][20], int N, int M)
{
for(int R=0;R<N;R++)
{
int SumR=0;
for(int C=0;C<M;C++)
SumR+=A[R][C];
cout<<"Row("<<R<<")="<<SumR<<endl;
}
for(int R=0;R<N;R++)
{
int SumR=0;
for(int C=0;C<M;C++)
SumR+=A[R][C];
cout<<"Row("<<R<<")="<<SumR<<endl;
}
}
Function to find sum of diagonal elements of a square matrix A
void Diagonal(int A[][20], int N, int &Rdiag, int &LDiag)
{
for(int I=0,Rdiag=0;I<N;I++)
Rdiag+=A[I][I];
for(int I=0,Ldiag=0;I<N;I++)
Ldiag+=A[N-I-1][I];
}
Function to find out transpose of a two dimensional array A
void Transpose(int A[][20], int B[][20],int N, int M)
{
for(int R=0;R<N;R++)
for(int C=0;C<M;C++)
B[R][C]=A[C][R];
}
Program for Accessing Two-Dimensional Array Elements
#include <iostream.h>
#include <conio.h>
int main ()
{
// an array with 5 rows and 2 columns.
int a[5][2] = { {0,0}, {1,2}, {2,4}, {3,6},{4,8}};
// output each array element's value
for ( int i = 0; i < 5; i++ )
for ( int j = 0; j < 2; j++ ) {
cout << "a[" << i << "][" << j << "]: ";
cout << a[i][j]<< endl;
}
return 0;
}
Expected Output
a[0][0]: 0
a[0][1]: 0
a[1][0]: 1
a[1][1]: 2
a[2][0]: 2
a[2][1]: 4
a[3][0]: 3
a[3][1]: 6
a[4][0]: 4
a[4][1]: 8
C++ Program to Store value entered by user in three dimensional array and display it.
#include <iostream.h>
#include <conio.h>
int main()
{
// This array can store upto 12 elements (2x3x2)
int test[2][3][2];
cout << "Enter 12 values: \n";
// Inserting the values into the test array
// using 3 nested for loops.
for(int i = 0; i < 2; ++i)
{
for (int j = 0; j < 3; ++j)
{
for(int k = 0; k < 2; ++k )
{
cin >> test[i][j][k];
}
}
}
cout<<"\nDisplaying Value stored:"<<endl;
// Displaying the values with proper index.
for(int i = 0; i < 2; ++i)
{
for (int j = 0; j < 3; ++j)
{
for(int k = 0; k < 2; ++k)
{
cout << "test[" << i << "][" << j << "][" << k << "] = " << test[i][j][k] << endl;
}
}
}
return 0;
}
Expected Output
Enter 12 values:
1
2
3
4
5
6
7
8
9
10
11
12
Displaying Value stored:
test[0][0][0] = 1
test[0][0][1] = 2
test[0][1][0] = 3
test[0][1][1] = 4
test[0][2][0] = 5
test[0][2][1] = 6
test[1][0][0] = 7
test[1][0][1] = 8
test[1][1][0] = 9
test[1][1][1] = 10
test[1][2][0] = 11
test[1][2][1] = 12