Bài giảng Introduction to Computer Programming (C language) - Chapter 5: Repetition Statements - Võ Thị Ngọc Châu

 Ho Chi Minh City University of Technology 
 Faculty of Computer Science and Engineering 
Chapter 5: Repetition Statements 
 Introduction to Computer Programming 
 (C language) 
 TS. Võ Thị Ngọc Châu 
 (chauvtn@cse.hcmut.edu.vn, 
 chauvtn@hcmut.edu.vn) 
 2017 – 2018, Semester 2 
Course Content 
 C.1. Introduction to Computers and 
 Programming 
 C.2. C Program Structure and its 
 Components 
 C.3. Variables and Basic Data Types 
 C.4. Selection Statements 
 C.5. Repetition Statements 
 C.6. Functions 
 C.7. Arrays 
 C.8. Pointers 
 C.9. File Processing 2 
 References 
 [1] “C: How to Program”, 7th Ed. – Paul 
 Deitel and Harvey Deitel, Prentice Hall, 2012. 
 [2] “The C Programming Language”, 2nd Ed. 
 – Brian W. Kernighan and Dennis M. Ritchie, 
 Prentice Hall, 1988 
 and others, especially those on the Internet 
 3 
Content 
 Introduction 
 while.. Statements 
 do..while.. Statements 
 for.. Statements 
 Nested Repetition Statements 
 continue Statements 
 break Statements 
 Summary 
 4 
 Introduction 
 Control statements in C 
  Sequence 
 Assignment 
 Function calling 
  Selection 
 if 
 if..else.. 
 switch..case.. 
  Repetition 
 for.. 
 while.. 
 do..while.. 
 5 
 Introduction 
 Given a void main() { 
 double positiveNumber[10] = {2, 1, 3, 10, 8, 3, 4, 5, 9, 12}; 
 set of n 
 int n = 10; 
 positive double minNumber = positiveNumber[0]; 
 int iteration = 1; 
 numbers, 
 while (iteration < n) { 
 find the if (minNumber <= positiveNumber[iteration]) 
 iteration = iteration + 1; 
 smallest 
 else { 
 one. minNumber = positiveNumber[iteration]; 
 iteration = iteration + 1; 
(Chapter 1 – 
 } 
Real code in C) } Control Statements for Repetition 
 } 
 6 
 Introduction 
 A repetition statement allows you to specify 
 that an action is to be repeated while some 
 condition remains true. 
 Example 1: Input validation 
  Ask a user to input a value 
  While his/her input value is invalid, ask him/her 
 to input a value. 
 Example 2: Search for any of you who didn’t 
 submit homework (i.e. no attachment exists) 
 Example 3: Count the number of occurrences 
 of an important keyword in a text 7 
 while.. Statements 
while () ; 
 false (= 0) 
while () { 
 ; true ( 0) 
 ; 
} 
 1. is evaluated. 
 2. If is true ( 0), are performed 
 and then go to step 3. Otherwise, i.e. if is false 
 (=0), go to step 4. 
 3. Go back to step 1. 
 4. End the repetition statement and move forward. 8 
while.. Statements 
 false (= 0) 
 i<=3 
 true ( 0) 
 printf(); 
 i++; 
 false (= 0) 
 i>=3 
 true ( 0) 
 printf(); 
 i++; 
 9 
while.. Statements 
Write a program to receive a natural number from a user. If an invalid 
value is entered, ask the user to input again until a valid one is obtained. 
 10 
while.. Statements 
 Given N, the number of the first natural numbers 
 greater than 0, calculate and print the total sum of 
 these N first natural numbers. 
 11 
while.. Statements 
 Given N, a natural number greater than 0, calculate and print the 
 factorial of N: N! = 1*2*..*N = (N-1)!*N 
 12 
 Given a natural number N 
while.. Statementsgreater than 0, list a series of 
 Fibonacci numbers smaller than N. 
 13 
 do..while.. Statements 
 do { 
 ; 
 ; true( 0) 
 } 
 while (); false(=0) 
 are always 
 1. are performed. 
 performed at least once! 
 2. is evaluated. 
 3. If is true ( 0), go to step 1. Otherwise, i.e. if 
 is false (=0), go to step 4. 
 4. End the repetition statement and move forward. 
 14 
do..while.. Statements 
 printf(); 
 i++; 
 true( 0) 
 i<=3 
 false(=0) 
 printf(); 
 i++; 
 true( 0) 
 i>=3 
 false(=0) 
do..while.. Statements 
Write a program to receive a natural number from a user. If an invalid 
value is entered, ask the user to input again until a valid one is obtained. 
 16 
do..while.. Statements 
 Given N, the number of the first natural numbers 
 greater than 0, calculate and print the total sum of 
 these N first natural numbers. 
 17 
do..while.. Statements 
 Given N, a natural number greater than 0, calculate and print the 
 factorial of N: N! = 1*2*..*N = (N-1)!*N 
 18 
Given a sequence of N numbers input sequentially 
by a user, find the minimum one. 
 19 
 for.. Statements 
 false (=0) 
 true ( 0) 
for (; ; ) ; 
for (; ; ) { 
 ; 
 ; 
} 20 
for.. Statements 
 false (=0) 
 true ( 0) 
1. is evaluated. 
2. is evaluated. 
3. If is true ( 0), are performed, 
 is evaluated, and then go to step 2. Otherwise, i.e. 
 if is false (=0), go to step 4. 
4. End the repetition statement and move forward. 21 
for.. Statements 
for (; ; ) ; 
is regarded as: 
 ; 
 while () { 
 ; 
 ; 
 } 
for (; ; ) { 
 ; 
 ; 
} 
is regarded as: 
 ; 
 while () { 
 ; 
 ; 
 ; 
 } 22 
 for.. Statements 
 i=1; 
 false (=0) 
 i<=3 
 true ( 0) 
 printf(); i++; 
No printing result exists due to a false value of the expression “i>=3”. 23 
for.. Statements 
 Given N, the number of the first natural numbers greater than 0, 
 calculate and print the total sum of these N first natural numbers. 
 24 
for.. Statements 
 Given N, a natural number greater than 0, calculate and print the 
 factorial of N: N! = 1*2*..*N = (N-1)!*N 
 25 
for.. Statements 
 Given a natural number N greater than 0, list all the squared numbers 
 smaller than the given number. 
 26 
for.. Statements 
 27 
while () { Nested Repetition 
 do { Statements 
 } 
 while (); 
 for(;;) { 
 } 
} 
for (; ; ) { A repetition statement 
 for (; ; ) { 
  can contain other 
 } 
 while () { repetition statements in 
 } many various 
} 
 combination ways. 
 28 
Nested Repetition Statements 
 Given a size of a window (N is an odd number and N>=5), 
 print a star of stars: diagonal and center lines 
 29 
Nested Repetition Statements 
 Given a natural number N greater than 0, print a 
 triangle full of stars. N is the height of the star triangle. 
 N = 4 
 30 
 Given a natural number greater than 0, 
Nested Repetitionprint two Statements squared isosceles triangles of 
 stars. 
 N=5 
 31 
continue Statements 
 the continue statement for skipping the 
 remainder of the body of a repetition 
 statement and proceeding with the next 
 iteration of the loop 
  while.. statements 
  do.. while.. statements 
  for.. statements 
 32 
continue Statements 
 The second loop has been skipped! 
 33 
break Statements 
 the break statement for exiting immediately 
 from certain control statements 
  switch..case statements 
  while.. statements 
  do.. while.. statements 
  for.. statements 
 34 
break Statements 
 All the loops from the second loop 
 have been skipped! 
 A corresponding repetition statement 
 is then ended. 
 35 
 Infinite Loops 
while (1) ; do { 
 ; 
while (1) { 
 ; 
 ; 
 } 
 ; 
 while (1); 
} 
 for (; 1;) 
for (; ;) ; 
 ; 
for (; ;) { 
 ; for (; 1;) 
 { ; 
 ;  
} ; 
 } 36 
Infinite Loops 
 37 
Put them all together 
 Write a program to compute an approximation of e with 
 a positive number N input by a user. Print the 
 approximated value and its difference from a commonly 
 used value which is 2.71828. It is given that: 0! = 1! = 1. 
 Natural number e is approximated: 
 38 
Put them all together 
 Write a program to compute an 
 approximation of the power x of e 
 where there is no use of a true value 
 of e. Accuracy of an approximation is 
 dependent on how large n is. 
 39 
Put them all together 
 Given problem: print the first NxN natural 
 numbers greater than 0 in a spiral-shaped 
 matrix with a given N. 
 Given N = 4, a printed spiral-shaped matrix is as follows: 
 1 2 3 4 0 
 12 13 14 5 12 
 11 16 15 6 
 10 9 8 7 
 Given N = 5, a printed spiral-shaped matrix is as follows: 
 1 2 3 4 5 0 
 16 17 18 19 6 16 
 15 24 25 20 7 24 
 14 23 22 21 8 
 13 12 11 10 9 40 
 N=10 
 N=9 
How to start the spiral at 
any given position (i,j)? 41 
 Summary 
 Three control statement types of repetition 
  while.. 
  do.. while.. 
  for... 
 Repeat actions in connection with conditions 
 break and continue statements 
  Important and helpful for controlling the loops in 
 repetition 
 Infinite loops 
  Check the conditions for repetition carefully 
 42 
Chapter 5: Repetition Statements 
 43