C on maateen

Reverse a Number or String in C

Wed, 11 Jun 2014 00:00:00 +0000

We, the C programmers, sometimes face a problem that we are to reverse a number or a string. On many online judges there are some problems like number reversion. On these cases, what will we do? We may consider the following code to reverse a number:

#include <stdio.h>
int main()
{
 int i, x = 12345, rev[5];
 for(i = 0; i < 5; i++){
 rev[i] = x % 10;
 x = x/10;
 printf("%d", rev[i]);
 }
 return 0;
}

Output:

54321

But this program can reverse only 12345. We can make it more efficient in this way:

strrev() Function in C

Tue, 10 Jun 2014 00:00:00 +0000

strrev function is defined in string.h header file. It reverses a given string. Its basic form is given below:

strrev(str);

Here str, a string, is a parameter of strrev() function. This function reverses this string. Please consider the following program:

#include <stdio.h>
#include <string.h>

int main()
{
 char str[100];
 gets(str);
 puts(strrev(str));
 return 0;
}

Input:

coder

Output:redoc

By using this program I mean strrev function, you can reverse any number or string. Hope you have understood the use of strrev function in C programming. Happy Coding!!!

strcpy() Function in C

Mon, 09 Jun 2014 00:00:00 +0000

Today we will talk about a string assignment operator. But before that, we will solve a problem. The problem is very easy. We have to copy/assign one string to another.

Suppose str1 & str2 are two strings. We have to copy/assign str2 to str1. We may try this as follows:

#include <stdio.h>

int main()
{
 char str1[15] = "Bangladesh";
 char str2[15] = "Bangla";
 str1 = str2;
 puts(str1);
 return 0;
}

But C doesn’t permit such kind of string-assignment. The thing, you can do, is writing the following program:

strlen() Function in C

Sun, 08 Jun 2014 00:00:00 +0000

strlen function is a very simple string library function defined in string.h header file. It returns the length of a given byte string. Here length means how many characters are containing in that string. But it’s noted that the null character will always be excluded from the length. Its basic form is given below:

strlen(string);

Here ‘string’ is the parameter of this function. This function returns an integer which indicates the length of string. Please consider the following example:

strncmp() Function in C

Sat, 07 Jun 2014 00:00:00 +0000

To understand this topic clearly, you should understand the strcmp function in C programming firstly. If you have understood already, then go ahead.

strncmp function is a variation of strcmp function. It compares a certain amount of characters of two null-terminated byte strings. The basic form is given below:

strncmp(str1, str2, n);

Here str1, str2 & n are the three parameters of this function. str1 & str2 are two null-terminated byte strings and n is an integer. n indicates the left-most n characters of str1. If str2 & the substring of str1 are equal, then strncmp function returns the value 0. Otherwise, it returns a numeric difference between the first mismatching characters based on ASCII value. If the value is negative, the substring of str1 is less than str2. If positive, the opposite result occurs. Now take a look at this example:

strcmp() Function in C

Fri, 06 Jun 2014 00:00:00 +0000

In C programming we need to compare two strings sometimes. In this case, what will you do? As a basic C programmer, you may write the following statement to compare two strings:

if(str1 == str2)
if(str1 == "Coder")

But unfortunately it’s invalid in C. You can’t compare two strings in such a way. Then what can you do? One thing you may do - compare character by character using a loop. This comparison will be run until a mismatch is found or any string of them terminates into a null character. Obviously I mean the following programs:

strncat() Function in C

Thu, 05 Jun 2014 00:00:00 +0000

If you understand the strcat function in C programming, then a question may appear in your subconscious (not sure) mind. That is about the concatenation of certain amount of two strings. For such kind of concatenation we can use another function defined in string.h header file. That is strncat function. Its basic form is given below:

strncat(str1, str2, n);

This function contains three parameters - str1 & str2 are two strings and n indicates an integer. Please consider the following program:

strcat() Function in C

Wed, 04 Jun 2014 00:00:00 +0000

Today we will talk something about string manipulation, defined in string.h header file. We use <string.h> header file when we want to use a function containing in string library functions. Among them, strcat function is one & very important.

We know that we can’t join two strings together by simple arithmetic addition. It means that the statements given below aren’t valid.

string = str1 + str2;
string = str3 + "Maksudur Rahman";

But sometime we need to concatenate two strings together. In those situations, what will we do? Obviously we will use strcat function in those case. strcat function concatenates two strings. Its basic form is given below: