compute occurrence of character in a string

write C Program print the frequency of a certain character in a string 

	#include <stdio.h>
	#include <string.h>
	int main(void) {
	printf("enter the string\n");
	char string[50];char c;int i=0;int counter=0;
	gets(string);
	printf("enter the character you want to compute its occurrence\n");
	scanf("%c",&c);
	while(string[i]!='\0')
	{
	if(string[i]==c){counter++;i++;}
	else {i++;continue;}
	}
	printf("%c occured %d times with frequency %f %c\n",c,counter,100*(float)counter/i,'%');
	return 0;
	}

view raw freq.c hosted with ❤ by GitHub

what is the output of this program

	#include <stdio.h>
	void f(int (*x)(int));
	int myfoo(int i);
	int (*foo)(int) = myfoo;
	int main()
	{
	f(foo(10));
	}
	void f(int (*i)(int))
	{
	i(11);
	}
	int myfoo(int i)
	{
	printf("%d\n", i);
	return i;
	}

view raw ptof.c hosted with ❤ by GitHub

output
10 segmentation fault

explanation

find the output

what will be the output of the following code 

	#include <stdio.h>
	int main(void) {
	int x=100;char y=3;float z=3.12;
	int *xp=&x;char *yp=&y;float *zp=&z;
	printf("%d\t%d\t%d\t%d\t%d\n",sizeof(NULL),sizeof(xp),sizeof(yp),sizeof(zp),sizeof("clu"));
	return 0;
	}

view raw szp.c hosted with ❤ by GitHub

output will be 
8  8  8  4
size of a pointer to any data type is type independent , size of pointer depends on your machine address bus.
sizeof("clu")  here "clu" is treated as array of characters ={'c','l','u','\0'}
so sizeof("clu") is 4 bytes

palindrome number

Write A program to check if a positive integer is palindrome or not

	#include <stdio.h>
	#include <math.h>
	int main()
	{
	int n;scanf("%d",&n);
	int digits=0;int reverse=0;
	int temp1=0;
	int temp2=0;
	if(n<=0){printf("enter positive enteger\n");}
	else
	{
	temp1=n;
	temp2=n;
	while(temp1!=0)
	{
	temp1/=10;
	digits++;
	}
	for(int i=digits-1;i>=0;i--)
	{
	reverse+=(temp2%10)*(pow(10,i));
	temp2/=10;
	}
	if(reverse==n){printf("palindrome\n");}
	else{printf("not palindrom\n");}
	}
	return 0;
	}

view raw palindrom.c hosted with ❤ by GitHub

Number of words in a string

Write a C function words(string) that accepts a string as input parameter and returns the number of words in this string 
as example
words("my name is mohamed") will return 4

	#include <stdio.h>
	#include <string.h>
	int words(char *s)
	{
	int i=0;
	int counter=0;
	if(strlen(s)==0){return 0;}
	else{
	while(*(s+i)!='\0')
	{
	if(*(s+i)==' '){counter++;i++;}
	i++;
	}
	return counter+1;
	}
	}
	int main(int argc, char **argv)
	{
	char statement[]="";
	printf("number of words are\n%d\n",words(statement));
	return 0;
	}

view raw no_of_words.c hosted with ❤ by GitHub

What will be the output of the following program

	#include <stdio.h>
	int main(int argc, char **argv)
	{
	char s[]="Egypt";
	for(int i=0;*("Egypt"+i)!='\0';i++)
	{
	printf("%c",s[i]);
	}
	return 0;
	}

view raw string.c hosted with ❤ by GitHub

the output is 
Egypt 
explanation 
string name is the base address of the string variable which is an array of characters

Even or Odd

Write a C program to check if any entered number is even or odd without the use of conditional statements (if,else)

	#include <stdio.h>
	int main(void) {
	printf("enter your number (assume it must be positive integer)\n");
	int input;
	scanf("%d",&input);
	char choise[2]={'E','O'};// O for Odd and E for Even
	printf("%d is %c",input,choise[input%2]);
	return 0;
	}

view raw evenorodd.c hosted with ❤ by GitHub

No loops

Write a C program to print the numbers from 1 to 10 without using any looping statements (for/while/do while)
also do not write printf() 10 times

	#include <stdio.h>
	int main()
	{
	static unsigned int counter=1;
	if(counter<=10)
	{
	printf("%d\t",counter);
	counter++;
	main();
	}
	return 0;
	}

view raw noloop.c hosted with ❤ by GitHub

convert to uppercase

Write a function upper() that accepts a string and converts all its characters into uppercase characters 
as example upper("c programming")=C PROGRAMMING

	#include <stdio.h>
	#include <string.h>
	#include <stdbool.h>
	bool is_upper(char x)
	{
	if((int)x>=65&&(int)x<=90)
	{
	return true;
	}
	return false;
	}
	char *upper(char *base)//passing array to a function that returns a pointer to char
	{
	while(*base!='\0')
	{
	if(is_upper(*base)||*base==' '){*base++;}
	else{*base-=32;base++;}
	}
	return base;
	}
	int main()
	{
	char array[20]="hE l lO";
	upper(array);
	puts(array);
	return 0;
	}

view raw upper.c hosted with ❤ by GitHub

reverse a string

Write a function reverse() that accepts a string and reverses it 

as example reverse("hello") would return "olleh"

	#include <stdio.h>
	#include <string.h>
	char* reverse(char *base)// passing array to a function that returns pointer to character
	{
	int i=0;
	int j=strlen(base)-1;
	char temp;
	while(i!=j)
	{
	temp=base[i];
	base[i]=base[j];
	base[j]=temp;
	i++;
	j--;
	}
	return base;
	}
	int main()
	{
	char array[5]="hello";
	puts(reverse(array));
	return 0;
	}

view raw reverse.c hosted with ❤ by GitHub

string of numbers

write a function that accepts string of numbers and converts it to digits 
as example convert("123")=123

	#include <stdio.h>
	void convert(char *base)// passing array to a function
	{
	while(*base!='\0')
	{
	*base-='0';//*base=*base-'0' will give you the numeric value of character number
	printf("%d",*base);
	base++;
	}
	}
	int main()
	{
	char num_char[5]="83461";
	convert(num_char);
	return 0;
	}

view raw convert.c hosted with ❤ by GitHub

Remove all blank spaces in a string

Write a C program to remove all the blank spaces from a string.

as example if string is "hello world , C programming" then the output will be "helloworld,Cprogramming"

	#include <stdio.h>
	#include <string.h>
	int main()
	{
	char input_string[100];char output_string[100];// two char arrays (two strings)
	printf("enter string with spaces\n");
	gets(input_string);// you can not use scanf() as it do not accept string with spaces
	int i=0;int j=0;
	while(input_string[i]!='\0')
	{
	if(input_string[i]!=' ')
	{
	output_string[j]=input_string[i];
	i++;
	j++;
	}
	else
	{
	i++;
	}
	}
	output_string[j]='\0';//terminate o/p string with null character
	printf("input string without spaces \n");
	puts(output_string);
	return 0;
	}

view raw remove.c hosted with ❤ by GitHub