COMP 102
Programming Fundamentals I
Presented by : Timture Choi
COMP102 Lab 09
1
2-D Array
E.g.


// declare a 2-D array of 30
uninitialized integers
int table[3][10];
 3 rows
 10 columns
0
1
2
0
1
2
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COMP102 Lab 09
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3
4
5
6
7
8
9
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---2
2-D Array
Accessing 2-D array
Syntax

array[row][column]
E.g.


table[1][2] = 5;
x = table[1][2];
table
COMP102 Lab 09
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1
2
0
1
2
3
4
5
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-5
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2-D Array Initialization
Two methods to initialize a 2-D array


int table[3][6] =
{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,
17,18};
int table[3][6] =
{{1,2,3,4,5,6},
{7,8,9,10,11,12},
{13,14,15,16,17,18}};
table
COMP102 Lab 09
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1
2
0
1
2
3
4
5
1
7
13
2
8
14
3
9
15
4
10
16
5
11
17
6
12
18
4
2-D Array Inputting Values
Use two for loops to access/process all the
elements of a 2-D array
E.g.
int total_row = 3, total_col = 6;
for (int row=0; row<total_row; row++)
for (int col = 0; col<total_col; col++) {
// assign value to an element of array
table[row][col] = row*col;
…
// assign value of an element to a variable
temp = table[row][col];
}
COMP102 Lab 09
5
Mathematical Functions
#include <math>

double log(double x)
 Natural logarithm

double log10(double x)
 Base 10 logarithm

double exp(double x)
 e to the power x

double pow(double x, double y)
 x to the power y

double sqrt(double x)
 Square root of x



double sin(double x)
double cos(double x)
double tan(double x)
 In radian argument
COMP102 Lab 09
6
Mathematical Functions
double ceil(double x)


Smallest integer not less than x
E.g.
 ceil(1.1) => 2
 ceil(-1.9) => -1
double floor(double x)


Largest integer not greater than x
E.g.
 floor(1.9) => 1
 floor(-1.1) => -2
<math.h> will not provide the round-off function
COMP102 Lab 09
double d; int i;
…
int i = (int) (d>0 ? d+0.5 : d-0.5);
7
Passing Arrays as Parameters
1-D


int func(int array[size], int size);
int func(const int array[size], int size);
2-D


int func(int array[row][col], int row, int col);
int func(const int array[row][col], int row, int col);
The “[ ]” in the formal parameter specification

Indicates that the variable is an array
It is a good practice to pass the dimension of the array as
another parameter
Arrays are always passed by reference

If the function must not change any element of the array
 const should be used
COMP102 Lab 09
8
SUMMARY
By the end of this lab, you should be
able to:

Declare and manipulate
 2-D arrays

Use mathematical functions provide by
 <math>

Pass an array to a function
 Normally
 With const keyword
COMP102 Lab 09
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