Prepared by
MURLI MANOHAR
PGT (COMPUTER SCIENCE)
KV,B.E.G., PUNE
•LOGICAL PROBLEM
BASED ON TWO
DIMENSIONAL ARRAY
Two-Dimensional Arrays
• Two-dimensional Array: a collection of a fixed
number of components arranged in two
dimensions
– All components are of the same type
• The syntax for declaring a two-dimensional
array is:
dataType arrayName[rowsize][colsize];
where rowsize and colsize are expressions yielding
positive integer values
Two-Dimensional Arrays (continued)
• The two expressions rowsize and
colsize specify the number of rows and
the number of columns, respectively, in the
array
• Two-dimensional arrays are sometimes called
matrices or tables
Two-Dimensional Arrays (continued)
A First Book of C++: From Here
To There, Third Edition
6
Accessing Array Components
• The syntax to access a component of a twodimensional array is:
arrayName[indexexp1][indexexp2]
where indexexp1 and indexexp2 are
expressions yielding nonnegative integer
values
• indexexp1 specifies the row position and
indexexp2 specifies the column position
Processing Two-Dimensional Arrays
•
A two-dimensional array can be processed in
three different ways:
1. Process the entire array
2. Process a particular row of the array, called row
processing
3. Process a particular column of the array, called
column processing
Processing Two-Dimensional
Arrays (continued)
• Each row and each column of a twodimensional array is a one-dimensional
array
• When processing a particular row or
column of a two-dimensional array
– we use algorithms similar to processing onedimensional arrays
Two-Dimensional Arrays
• Two-dimensional arrays are stored in row
order
– The first row is stored first, followed by the
second row, followed by the third row and so
on
• When declaring a two-dimensional array as
a formal parameter
– can omit size of first dimension, but not the
second
• Number of columns must be specified
Initialisation of 2D Array
#include <iostream>
int main()
{
int _2DArray[5][6] = { { 1, 2, 3, 4, 5, 6},
{ 7, 8, 9, 0, 1, 2},
{ 3, 4, 5} };
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 6; j++)
{
cout << _2DArray [i][j];
}
cout << endl;
}
cout << endl;
return 0;
}
OUTPUT
1
7
3
0
0
2
8
4
0
0
3
9
5
0
0
4
0
0
0
0
5
1
0
0
0
6
2
0
0
0
• Write a user function named Lower_half()
which takes a two dimensional array A, with
size N rows and N columns as argument and
pronts the lower half of the array.
2
7
2
0
3
3
1
5
1
4
1
5
7
5
9
5
3
8
0
1
0
1
1
1
5
if A is
void Upper_half(int b[ ][10 ], int N)
{ int i, j;
for (i = 0 ; i<N; i++)
{
for (j =0 ; j < N; j++)
{
if (I > = j)
cout<< b[i][j] <<“ “;
else
cout << “ “;
}
cout<< “ \n “;
}
}
• The output will be
2
7
1
2
5
7
0
1
5
0
3
4
9
1
5
• Write a function int ALTERSUM ( int B[][5], int N, int M)
in c++ to find and return the sum of elements from all
alternate elements of a two-dimensional array starting
from B[0][0].
• Sol. int ALTERSUM(int B[ ][3], int N, int M)
{
int sum = 0;
for (int I = 0; I<N; I++)
for (int J = 0; J < M; J++)
{
if( I + J ) %2 = = 0)
sum = sum + B[I][J];
}
return sum;
}
• Write a function in c++ which accepts a 2D array of integers
and its size as arguments and displays the elements which
lie on diagonals.
const int n = 5;
void Diagonals( int A[n][n], int size)
{
int i, j;
cout << “ Diagonal One”;
for (i=0 ; i<n; i++)
cout << A[i][i]<< “ “;
cout<< “Diagonal Two”;
for (i = 0; i<n; i++)
cout<<A[i][n-(i+1)]<< “ “
}
• Write a function in c++ which accepts a 2D array of integers and its
size as arguments and displays the elements of middle row and the
elements of middle column.
const int S = 5;
void DisplayMidle( int A[S][S], int S)
{
int mid = S/2;
int i;
cout << “ \n Middle row”;
for (i=0 ; i<S; i++)
cout << A[ mid ][ i ]<< “ “;
cout<< “ \n Middle Column ”;
for (i = 0; i<S; i++)
cout<<A[i][ mid ]<< “ “
cout << endl;
}
THANK YOU