13 More on Loops.pptx - Topic 13 More on Loops 1 Computing...

Topic 13
More on Loops
1

Computing Total in Loop
 Suppose we want to find the total of numbers 1
to 4.
 We use the for statement to generate the
numbers:
for ( int number = 1; number <= 4; number+
+ )

To find the total, we start with a total of 0 and
keeping adding each number to the total until we
get the total of all the numbers.
2

Computing Total in Loop
total
numbe
r
0
0 + 1 = 1
3
1
2
3
4
5 (exit
loop)

Computing Total in Loop
total
numbe
r
0
1
1 + 2 = 3
4
1
2
3
4
5 (exit
loop)

Computing Total in Loop
total
numbe
r
0
1
3 + 3 = 6
3
5
1
2
3
4
5 (exit
loop)

Computing Total in Loop
total
numbe
r
0
1
2
3
4
5 (exit
loop)
6
6 + 4 =
10
1
3
6

Computing Total in Loop
Total
Numbe
r
7
1
2
3
4
5 (exit
loop)
0
6
10
1
3

Computing Total in Loop
// initialise total to 0 once before loop
starts
for ( int number = 1; number <= 4; number++ )
{
// add each number to total in loop body
}
// display the total once after the loop
ends
8

Computing Total in Loop
int total = 0;
for (int number = 1; number <= 4; number++
)
{
total += number;
}
cout << " Total of 1 to 4 is " << total <<
endl;
total number number <= 4
0 1 true
(0+1 = ) 1 2 true
(1+2 = ) 3 3 true
(3+3 = ) 6 4 true
(6+4 = ) 10 5 false
9

Computing Total in Loop
 Example – adding a set of n numbers:
int n,
total = 0;
cout << "Enter number of values to add: ";
cin >> n ;
for ( int count = 1; count <= n ; count++ )
{
cout << "Enter number to add: ";
cin >> number;
total += number;
}
cout << " The total is " << total << endl;
10

Computing Total in Loop
11

Computing Product in Loop
 Example:
int n, product = 1; // cannot initialise to 0
cout << "Enter number of values to multiply: ";
cin >> n;
for ( int count = 0; count < n; count++ )
{
cout << "Enter number to multiply: ";
cin >> number;
product *= number;
}
cout << "The product is " << product << endl;
12

Computing Product in Loop
13

14
Looping Applications
In this section, we examine four common
applications for loops: summation, product, smallest
and largest. Although the uses for loops are virtually
endless, these problems illustrate many common
applications.
Summation
Powers
Smallest and Largest
Topics discussed in this section:

15
Summation and Product Loops

16
FIGURE 6-23 Smallest and Largest Loops

17
To find the largest, we need to initialize the smallest variable to a very small
number, such as INT_MIN.
To find the smallest, we need to initialize the result to a very large number,
such as INT_MAX.
Note

Finding largest value in Loop
 Example – finding largest in a set of n numbers:
int n,
largest = INT_MIN;
cout << "Enter number of values to compare: ";
cin >> n
for ( int count = 1; count <= n ; count++ )
{
cout << "Enter number to compare: ";
cin >> number;
if(largest < number)
;
largest = number
}
cout << " The largest number is " << largest << endl;
18

Finding smallest value in Loop
 Example – finding smallest in a set of n numbers:
int n,
smallest = INT_MAX;
cout << "Enter number of values to compare: ";
cin >> n ;
for ( int count = 1; count <= n ; count++ )
{
cout << "Enter number to compare: ";
cin >> number;
if(smallest > number)
smallest = number
}
cout << " The smallest number is " << smallest << endl;
19

Case Study 1
 Problem:
A company has several employees whose pay
must be calculated. The total pay for all
employees must also be calculated.
 Understand the problem:
1.