Lecture 15: Control Flow (cont)
Lecture Contents:
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Design and implementation of programs
illustrating linear algorithms, branch algorithms
and loop algorithms.
Training session on statement level control
structures (statements)
Demo programs
Exercises
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Function getint(nmin, nmax)
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Build an integer valued function with two formal
parameters int getint(int nmin, int nmax);
to return an integer that is in the range specified
by the function’s two arguments nmin and nmax.
A loop would repeatedly prompt the user for a
value in the desired range.
See source text on back page of handout
Edit, compile and run the program
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Function getint(nmin, nmax)
#include <iostream>
using namespace std;
int getint(int, int);
void main()
{
for (int k=1; k<=3; k++) {
cout << "\nDriver program testing function getint(p1,p2)";
cout << "\nYou entered value " << getint(10, 20) << "\n";
}
}
int getint(int nmin, int nmax)
{
int inval, errorflag;
do
{
errorflag = 0;
cout<<"\nEnter integer in range from " << nmin << " to "<< nmax;
cin >> inval;
if (inval < nmin || inval > nmax)
{
errorflag = 1;
cout <<"\n Number " << inval << "not in range";
}
} while (errorflag);
return inval;
}
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Pythagorean triples
Input: two positive integer values m, n; m>n
Output: side1 = m2 – n2
side2 = 2mn
hypotenuse = m2 + n2
Task: To compute 5 Pythagorean triples
Task: To compute k Pythagorean triples
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Pythagorean triples
The solution:
void main()
{
int I; int m, n;
for (i=1; i<=5; i++)
{ cin >> m>> n;
side1 = …
side2 = …
hypotenuse = …
cout << ‘\n’ << side1 << ‘ ‘ << side2 < ‘ ‘ << hypotenuse;
}
}
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Pythagorean triples
The solution:
void main()
{
int I; int m, n; int k;
cout << “\n Enter value for k”; cin >> k;
for (i=1; i<=k; i++)
{ cin >> m>> n;
side1 = …
side2 = …
hypotenuse = …
cout << ‘\n’ << side1 << ‘ ‘ << side2 < ‘ ‘ << hypotenuse;
}
}
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Euclid’s algorithm – GCD of
two positive integer numbers
Input: two positive integer values m, n
Algorithm: loop division m%n while the remainder is != 0
int m, n, rem, gcd;
cin >> m >> n;
while ( (rem = m%n)!= 0)
{
m = n;
n = rem;
}
gcd = n;
cout << “\nGCD is =“ << gcd << endl;
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Trivial algorithm – GCD of
two positive integer numbers
Input: two positive integer values m, n
Algorithm: loop – looking for common divisors of m and n
int m, n, i=1, gcd;
cin >> m >> n;
while ( i<m || i<n )
{
if (m%i==0 && n%i==0) {
i++;
}
cout
<<
gcd = I;
}
gcd;
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Practical Tasks
Write a program that calculates the
factorial function N! = 1 * 2 * … * N.
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Practical Tasks
Write a program to display the first 10
numbers that are part of the Fibonacci
sequence. (The Fibonacci sequence
begins 1, 1, 2, 3, 5, 8, …, where each
new number in the sequence is found
by adding the previous two numbers in
the sequence.)
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Practical Tasks
Write a program to display the first n (n
is input value) numbers that are part of
the
Fibonacci
sequence.
(The
Fibonacci sequence begins 1, 1, 2, 3, 5,
8, …, where each new number in the
sequence is found by adding the
previous two numbers in the
sequence.)
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Practical Tasks
Write a program to display all the numbers
between 1 and 100 that are part of the
Fibonacci sequence. (The Fibonacci
sequence begins 1, 1, 2, 3, 5, 8, …, where
each new number in the sequence is found
by adding the previous two numbers in the
sequence.)
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More on loop statement(s)
Extract from Friedman/Koffman, chapter 5
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Repetition and Loop Statements
Chapter 5
Exercise 15.1
Build programs based on loop algorithms using the
repetition statements: counter controlled and/or
logically controlled loops with for, while and do-while
statements;
Problem:
Test the function int getint(int nmin, int nmax)
to return an integer that is in the range specified by its
two arguments min and nmax
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Exercise 15.2
Build programs based on loop algorithms
using the repetition statements: counter
controlled and/or logically controlled loops
with for, while and do-while statements;
Problem: Character I/O using end file
controlled loop
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Exercise 15.3
Build programs based on loop algorithms
using the repetition statements: counter
controlled and/or logically controlled loops
with for, while and do-while statements;
Problem: Pythagorean triples
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Exercise 15.4
Build programs based on loop algorithms using
the repetition statements: counter controlled
and/or logically controlled loops with for,
while and do-while statements;
Problem: Greatest Common Divisor (Euclid’s
algorithm int gcdi(int m, int n);
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Exercise 15.4
Build programs based on loop algorithms using the
repetition statements: counter controlled and/or
logically controlled loops with for, while and
do-while statements;
Problem: Factorial function int facti(int n);
n! = 1 * 2 * . . . * n
0! = 1
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Before lecture end
Lecture:
Control Flow. Repetition and loop structures
More to read:
Friedman/Koffman, Chapter 05
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Thank You
For
Your Attention!
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