control structures - wordpress.comapr 02, 2011  · control structures nguyen dung falculty of...

Control Structures Nguyen Dung

Falculty of Information Technology

Hue University of Science

Content

Selection

if statement

switch statement

Iteration (loop)

for statement

while statement

do … while statement

Jump:

break

continue

return

goto 2

if statement

Syntax 1st:

if ( expression ) {B;}

exp

B

nonzero

zero

3

if statement

Example:

int a = 5, b = 9, max;

max = a;

if ( max < b ){

max = b;}

printf(“Max is: %d”,max);

Max is: 9

if (max < b)

max = b;

4

if statement

Syntax 2nd:

if ( exp ) {B1;}

else {B2;}

exp

B1

nonzero zero

B2

5

if statement float a, b, x;

printf(“a = ");scanf("%f",&a);

printf(“b = ");scanf("%f",&b);

if (a == 0 ){

if ( b != 0 )

printf(“Equation hasn’t root.”);

else

printf(“Equation has countless root.”);

}

else{

x = -b/a;

printf(“Root of equation is x = %f”,x);

}

a = 2

b = 6

Root of equation is x = -3.00

6

Excercises

1. Xác định xem một số nguyên là chẵn hay lẻ.

2. Xác định học lực dựa vào điểm trung bình của sinh viên, biết:

3. Xác định số có giá trị lớn hơn trong hai số thực a, b theo 2 cách: sử dụng lệnh if và không sử dụng lệnh if

4. Hiển thị một số tự nhiên bất kì từ 0 đến 9 dưới dạng chữ.

ĐTB [0, 4) [4, 5) [5, 6.5) [6.5, 8) [8, 9) [9, 10]

Học lực Kém Yếu Trung bình Khá Giỏi Xuất sắc

7

exp==

exp1

exp==

exp2

…

exp==

expn

B0;

B1;

B2;

Bn;

Zero

Zero

Zero

Zero

Non-Zero

Non-Zero

Non-Zero

8

switch statement

Syntax:

switch (exp)

{

case (exp1):

B1; break;

case (exp2):

B2; break;

...

case (expN):

BN; break;

[default: B0;]

}

expression

Constant-expression

9

Example:

void main()

{ int x;

printf("Nhap so: ");

scanf("%d", &x);

switch(x){

case 0: printf(“Khong”);break;

case 1: printf(“Mot”);break;

case 2: printf(“Hai”);break;

case 3: printf(“Ba”);break;

case 4: printf(“Bon”);break;

case 5: printf(“Nam”);break;

case 6: printf(“Sau”);break;

case 7: printf(“Bay”);break;

case 8: printf(“Tam”);break;

case 9: printf(“Chin”);break;

}

getch();

}

Nhap so: 6

Sau

10

while .. do statement

Syntax:

while (exp)

{

B;

} exp B;

Zero Non-Zero

11

Example

Find “greatest common divisor” of a and b.

Then find “least common multiple” of a and

b

Input: a, b

Output: GCD(a,b) and LCM(a,b)

Method:

𝐺𝐶𝐷 𝑎, 𝑏 =

𝑎 𝑖𝑓 𝑏 = 𝑎

𝐺𝐶𝐷 𝑎 − 𝑏, 𝑏 𝑖𝑓 𝑎 > 𝑏

𝐺𝐶𝐷 𝑎, 𝑏 − 𝑎 𝑖𝑓 𝑎 < 𝑏

𝐺𝐶𝐷 𝑎, 𝑏 =𝑎𝑏

𝐿𝐶𝑀 (𝑎, 𝑏)

𝐺𝐶𝐷 𝑎, 𝑏 = 𝑎 𝑖𝑓 𝑏 = 0

𝐺𝐶𝐷 𝑏, 𝑏 𝑚𝑜𝑑 𝑎 𝑖𝑓𝑏 ≠ 0

12

Implement unsigned int x, y, a, b;

printf("Nhap x, y: ");

scanf("%d,%d", &x, &y);

if (x == 0 && y == 0)

printf(“Both a and b are 0\n");

else if (x * y == 0){

printf(“GCD(%d,%d) is: %d\n", x, y, x+y);

}

else{

a = x;b = y;

while(a != b){

if (a > b)

a -= b;

else

b -= a;

}

printf(“GCD(%d,%d): %d\n", x, y, a);

printf(“LCM(%d,%d) is: %d\n",x, y,(x*y)/a);

}

unsigned int r = 0;

while(b!=0){

r = a % b;

a = b;

b = r;

}

13

do .. while statement

Syntax:

do

{

B;

}

while (exp);

exp

B;

Zero

Non-Zero

Different with

while statement??? 14

Example

#include <stdio.h>

#include <conio.h>

void main()

{

int x; char c;

do{

printf(“\nEnter x: ”);

scanf(“%f”, &x);

if (x%2==0){

printf(“%d is even”,x);

}

else

printf(“%d is odd”,x);

printf(“\nPress ESC to exit... ”);

c = getch();

} while (c!=27);

}

Enter x: 6

6 is even

Press ESC to exit...

Enter x: 7

7 is odd

Press ESC to exit...

15

for statement

Syntax:

for(exp0;exp1;exp2)

{

B;

} exp1

exp0;

Zero

Non-Zero

B;

exp2; 16

Example

Find the following sum:

S = 1 + 2 + 3 + ... + n = 𝒊𝒏𝒊=𝟏

Input: n

Output: sum of n number from 1 to n

Method:

s = 0;

For i = 1 to n do

s = s + i;

17

Implement

#include <stdio.h>

#include <conio.h>

void main()

{

int n, s=0;

printf(“Enter n: ");

scanf("%d", &n);

for(int i = 1; i <= n; i++)

s = s + i;

printf(“Sum is: ", s);

getch();

}

Enter n: 6

Sum is: 21

18

break, continue, goto

The break command allows you to terminate

and exit a loop (that is, do, for,

and while) or switch command from any point

Example

int s = 0;

for(int i = 0; i <= 10; i++){

if (i == 5)

break;

s = s + i;

}

printf(“s = %d”,s);

s= ???

19

break, continue, goto

The continue statement jumps the next

loop.

Example

int s = 0;

for(int i = 0; i <= 10; i++){

if (i == 5)

continue;

s = s + i;

}

printf(“s = %d”,s);

S = ???

20

break, continue, goto

Goto: self-study

21

return

The return statement:

terminates the execution of a

function

or return a result(address or value)

to the calling function and exit

function.

Syntax:

return exp;

22

Warning Homework

Please visit website

to get it.

23

Questions

24

The end

25