This document provides information and examples on how to write functions to manipulate 2D arrays in C++ for computer science exams. It discusses 2D array function headers, passing 2D arrays as arguments, and examples of functions to print, calculate sums, and manipulate elements of 2D arrays, such as printing diagonals, triangles, and alternate elements. It concludes with practice questions on writing functions to calculate sums of upper, lower and alternate elements of a 2D array.

2. GET 100% MARKS IN
COMPUTER SCIENCE
2-D ARRAY FUNCTION
WRITING QUESTION
EXAM WEIGHTAGE-3/4MARKS
VIDEO 1

3. FUNCTION HEADER
Void nameof function(int arr[][5], int r,int c)
{
//write your function code here
}
Argument 1 : int arr[][5] for passing 2-d array to
function (first index(row index) no. will be left
blank but it is mandatory to pass the second
index(col index) no. )
Argument 2 : int r to pass the row size of 2d array
Argument 3 : int c to pass the column size of 2d
array

4. TYPE OF QUESTION
1. To calculate sum of particular elements of a 2d array
2. To print particular elements of a 2 d array
3. To update a 2d array in a particular manner
4. To swap/shift the elements of a 2d array in a particular manner

5. LOGIC FOR PRINTING A 2D ARRAY
Void PrintArray(int arr[][4],int r, int c)
{
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
cout<<arr[i][j]<<“t”;
}
cout<<“n”;
}
}
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OUTPUT

6. LOGIC FOR CALCULATING SUM OF A 2D ARRAY
Void PrintArray(int arr[][4],int r, int c)
{
int sum=0;
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
sum=sum+ arr[i][j];
}
}
cout<<“Sum of matrix elements : ”<<sum;
}
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OUTPUT
Sum of matrix elements : 136

7. SQUARE MATRIX
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10 11 12 13
20 21 22 23
30 31 32 33
Square matrix : in which no of row(r) = no of col(c)
1.)Main Diagonal : arr[0][0], arr[1][1], arr[2][2], arr[3][3]
Condition for main diagonal : (i==j)
Off diagonal: arr[0][3], arr[1][2], arr[2][1], arr[3][0]
Condition for off diagonal : (i+j)==r-1 / (i+j)==c-1
Upper triangle : (above main diagonal)
condition (i<=j)
Lower Triangle: (below main diagonal)
condition(i>=j)
Main diagonalOFF Diagonal

8. 1.) Write a function printdiagonal(int arr[][4],int r,int c) to print
diagonals of a 2d array
Void printdiagonal(int arr[][4],int r,int c)
{
cout<<“Diagonal ONE : ”;
for(int i=0;i<r;i++)
{
cout<<arr[i][i]<<“t”;
}
cout<<“nDiagonal TWO :”;
for(int i=0;i<r;i++)
{
Cout<<arr[i][r-1-i];
}
}
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OUTPUT:
DIAGONAL ONE : 1 6 11 12
DIAGONAL TWO : 4 7 10 13

9. 2.) Write a function printdsum(int arr[][4],int r,int c) to print
sum of diagonals of a 2d array
Void printdsum(int arr[][4],int r,int c)
{
int d1sum=0,d2sum=0;
for(int i=0;i<r;i++)
{
d1sum=d1sum+arr[i][j];
}
for(int i=0;i<r;i++)
{
d2sum=d2sum+arr[i][r-1-i];
}
cout<<“Main Diagonal Sum : ”<<d1sum;
cout<<“nOff Diagonal Sum : ”<<d2sum;
}
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OUTPUT:
Main Diagonal Sum : 34
Off Diagonal Sum : 34

10. 3.) Write a function printupper(int arr[][5],int r,int c) to print Upper
triangle elements of a 2d array
Void printdiagonal(int arr[][5],int r,int c)
{
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
if(i<=j)
cout<<arr[i][j]<<“t”;
else
cout<<“t”;
}
cout<<“n”;
}
}
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OUTPUT:
1 2 3 4
6 7 8
11 12
16

11. 4.)Write a function printlower(int arr[][5],int r,int c) to print
Upper triangle elements of a 2d array
Void printdiagonal(int arr[][4],int r,int c)
{
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
if(i>=j)
cout<<arr[i][j]<<“t”;
else
cout<<“t”;
}
cout<<“n”;
}
}
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OUTPUT:
1
5 6
9 10 11
13 14 15 16

12. 5.) Write a function printalternate(int arr[][5],int r,int c)
to print Upper triangle elements of a 2d array
Void printdiagonal(int arr[][4],int r,int c)
{
for(int i=0;i<r;i++)
{
for(int j=0;j<c;j++)
{
if(i+j%2==0)
cout<<arr[i][j]<<“t”;
else
cout<<“t”;
}
cout<<“n”;
}
}
Condition :
i+j = even
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30 31 32
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11
20 22
31

13. PRACTICE QUESTION
Q.1) Write a function printuppersum(int arr[][5],int r,int c) to calculate and print sum
Upper triangle elements of a 2d array
Q.2) Write a function printlowersum(int arr[][5],int r,int c) to calculate and print sum of lower triangle
elements of a 2d array
Q.3) Write a function printalternatesum(int arr[][5],int r,int c) to calculate and print sum of alternate
elements of a 2d array

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