strcspn() In C

Purpose Of strcspn()

strcspn() is one of the inbuilt string function in c programming which is used to returns the number of characters at the beginning of first string that do not occur in the second string.

How strcspn() Works

The following diagram clearly illustrate the working principle of strcspn() inbuilt string function in C.

In the above diagram strcspn() takes two parameters say str1 and str2. Both parameters are string type. strcspn() will take a first character from a string str1 and scans the string str2 to find the occurance of a first character in str1. If a character exist, strcspn() will return 0 and terminate. If not strcspn() will set count to 1 and take a second character of a string str1 and scans the string str2 to find the occurance of a second character in str1. If a character exist, strcspn will return 1 and terminate. If not, strcspn() will set count to 2 and the process continue until any one of a character from str1 matches str2.

Syntax Of strcspn()

• strcspn() will accepts two parameters
• Both parameters must be a strings.
• To use strcspn() inbuilt string function in C, we need to declare #include<string.h> header file.

strcspn(str1, str2);

C Program - strcspn()

Let us work through strcspn() function. In the following program we will find the occurance of str1 characters in str2 by using strcspn() inbuilt string function.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[20] = "2braces";
char str2[20] = "latest";
int len;
len = strcspn(str1, str2);
printf("Number of characters are %d ", len);
return 0;
}

Number of characters are 3

C Program - Without strcspn()

In the following program we will find the occurance of str1 characters in string str2 without using any inbuilt string functions.

#include <stdio.h>
#include<string.h>
int main()
{
char str1[20] = "2braces";
char str2[20] = "latest";
int len = 0, i, j;
for(i=0; str1[i] !='\0'; i++)
{
for(j=0; str2[j] !='\0'; j++)
{
if(str1[i] == str2[j])
break;
}
if(str1[i] == str2[j])
break;
len++;
}
printf("Number of characters are %d ", len);
return 0;
}

Number of characters are 3

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