Algorithm Diary

Program Control : Repetition

Repetition used to repeat one or more instruction for a certain amount of time. There are kinds of repetitions :

-         - For

-          -While

-         - Do – While

The Use of For

for(exp1; exp2; exp3) statement;

exp1 :  initialization

exp2 :  conditional

exp3 :  increment or decrement

Example of For

#include<stdio.h>

int main()

{

    int x;

    for( x = 1 ;  x <= 10 ;  x++ ) printf( "%d\n", x );

    return(0);

}

The Use of While

while (exp) statements;

or:

while(exp){

  statement1;

  statement2;

   …..

}

Example of While

int counter = 1;

while ( counter <= 10 ) {

     printf( "%d\n", counter );

     ++counter;

}

The Use of Do - While

do{

    < statements >;

} while(exp);

Example of Do - While

int counter=0;

do {

     printf( "%d  ", counter );

  ++counter;

} while (counter <= 10);

                 Pointers and Arrays

Pointer is a variable that store the address of another variable, the operators are : * (content of) and &(address of).

Example:

int i, *ptr;

ptr = &i;

To assign a new value to the variable pointed by the pointer:

*ptr = 5;  /* means i=5 */

An array is a collection of data items, all of the same type, accessed using a common name.

Example :

int A[10];

Assigning Value to an element
Example : A[6] = 15; A[3] = 27

Array Program Examples

#include <stdio.h>

void main()

{

  int i;

  int list_int[10];

  for (i=0; i<10; i++){

    list_int[i] = i + 1;

    printf( "list_int[%d] init with %d.\n", i, list_int[i]);

  }

} 

There are two types of Array:
- One Dimensional Array
- Two Dimensional Array

Example of One Dimensional Array

#include<stdio.h>

int SIZE = 5;

void main() {

  int i, j;

  int n[SIZE] = {15, 9, 1, 7, 5};

  for( i=0 ; i<= SIZE ; i++) {

  printf("%5d ", n[i]);

  for ( j=1; j<=n[i] ; j++) printf("%c","*");

  printf("\n");

  }

}

Example of Two Dimensional Array
int a[3][4];