C Linux Code for user defined string routines strcmp strcpy strcat strrev strstr strlen

String library function strcmp, strcpy, strcat, strrev, strstr,strlen without using built in library function in one place

 //1.strStr: c code for user defined function to find a string from multiple strings
#include<stdio.h>

int compare_string(char*, char*);

int main()
{
    char first[100], second[100], result;

    printf("Enter first string\n");
    gets(first);

    printf("Enter second string\n");
    gets(second);

    result = compare_string(first, second);

    if ( result == 0 )
       printf("Both strings are same.\n");
    else
       printf("Entered strings are not equal.\n");

    return 0;
}

int compare_string(char *first, char *second)
{
   while(*first==*second)
   {
      if ( *first == '\0' || *second == '\0' )
         break;

      first++;
      second++;
   }
   if( *first == '\0' && *second == '\0' )
      return 0;
   else
      return -1;
}

 /*
OUTPUT:
-bash-3.2$ vi strStr.c
-bash-3.2$ gcc strStr.c
/tmp/ccUUzk8E.o: In function `main':
strStr.c:(.text+0x27): warning: the `gets' function is dangerous and should not be used.
-bash-3.2$ ./a.out
Enter few strings:
all is well
Enter the string to search:
code
NOT Present
-bash-3.2$ ./a.out
Enter few strings:
all is well
Enter the string to search:
all
Present at location :1
-bash-3.2$ ./a.out
Enter few strings:
all is well
Enter the string to search:
is
Present at location :5
-bash-3.2$ ./a.out
Enter few strings:
all is well
Enter the string to search:
well
Present at location :8
-bash-3.2$ ./a.out
Enter few strings:
all is well
Enter the string to search:
ll
Present at location :2
-bash-3.2$
*/

 //2. strCmp:  c code for user defined function to compare two strings
//finding a string in strings array
#include<stdio.h>
int strStr(char *str1, char *str2);
int main()
{
char str1[100],str2[10];
printf("Enter few strings:\n");
gets(str1);
printf("Enter the string to search:\n");
gets(str2);

 int result;
result=strStr(str1,str2);
if(result==0)
printf("Equals\n");
else
printf("NOT Equals\n");

 //return 0;
}

 int strStr(char *str1, char *str2)
{
while(*str1==*str2)
{
if(*str1=='\0' || *str2=='\0')
break;

 str1++;
str2++;
}

 if(*str1=='\0' && *str2=='\0')
return 0;
else
return -1;
}

/*
OUTPUT:
-bash-3.2$ gcc strCmp.c
/tmp/ccyAmuWc.o: In function `main':
strCmp.c:(.text+0x27): warning: the `gets' function is dangerous and should not be used.
-bash-3.2$ ./a.out
Enter few strings:
india
Enter the string to search:
india
Equals
-bash-3.2$ ./a.out
Enter few strings:
india
Enter the string to search:
in
NOT Equals
-bash-3.2$ ./a.out
Enter few strings:
in
Enter the string to search:
india
NOT Equals
-bash-3.2$ india
-bash: india: command not found
-bash-3.2$ ./a.out
Enter few strings:
India
Enter the string to search:
india
NOT Equals
-bash-3.2$

 */
//3. strLen:c code for user defined function to find length of a string
#include<stdio.h>
int main()
{
char arr[20];
printf("Enter a string:\n");
gets(arr);

 int result;
result=strLen(arr);
printf("Length of the string is:%d\n",result);
return 0;
}

 int strLen(char *str)
{
char *tmp;
tmp=str;
while(*tmp)
{
tmp++;
}
return (tmp-str);
}
/*
-bash-3.2$ ./a.out
Enter a string:
India
Length of the string is:5
-bash-3.2$ ./a.out
Enter a string:
India is great
Length of the string is:14
*/

//4. strCpy:C code for user defined function to copy one string to another
#include<stdio.h>
void strCpy(char *p2, char *p1);
int main()
{
char str1[20];
char str2[20];

 printf("Enter a string:\n");
gets(str1);

 strCpy(str2,str1);
printf("Copied string is:%s\n",str1);
return 0;
}

 void strCpy(char *p2, char *p1)
{
while(*p1!='\0')
{
*p2=*p1;
p2++;
p1++;
}
*p2='\0';
}
/*
OUTPUT:
-bash-3.2$ gcc strCpy.c
/tmp/ccaP29bY.o: In function `main':
strCpy.c:(.text+0x24): warning: the `gets' function is dangerous and should not be used.
-bash-3.2$ ./a.out
Enter a string:
india
Copied string is:india
-bash-3.2$ ./a.out
Enter a string:
hello india
Copied string is:hello india
-bash-3.2$

 */

 //5. strRev: C code for user defined function to reverse a string

 //strRev"User defined function to reverse a string
#include<stdio.h>
#include<string.h>
void strRev(char *arr1);

 int main()
{
char arr1[20];
printf("Enter a string to be reversed:\n");
gets(arr1);
strRev(arr1);
printf("Reversed string is :%s\n",arr1);
return 0;
}

 void strRev(char *arr1)
{
   char *begin;
   char *end;
   char temp;
   begin = arr1;
   end = arr1;

    int length, i;
   length=strlen(arr1);

  for ( i = 0 ; i < (length) - 1  ; i++ )
 end++;

    for ( i = 0 ; i < length/2 ; i++ )
   {
      temp = *end;
      *end = *begin;
      *begin = temp;

       begin++;
      end--;
   }
}

 /*OUTPUT:

 -bash-3.2$ ./a.out
Enter a string to be reversed:
hello
Reversed string is :olleh
-bash-3.2$ ./a.out
Enter a string to be reversed:
hello india
Reversed string is :aidni olleh
-bash-3.2$ ./a.out
Enter a string to be reversed:
a
Reversed string is :a
-bash-3.2$

 */

 //6. strCat: C code for user defined string concatenation of two strings
#include<stdio.h>
void strCat(char * str1, char *str2);
int main()
{
char str1[20];
char str2[20];
printf("Enter first string:\n");
gets(str1);

 printf("Enter second string to concatenate to first:\n");
gets(str2);

 strCat(str1,str2);
printf("Conacatenated String is:%s\n",str1);

 return 0;
}

 void strCat(char *p11, char *p22)
{
char *p1, *p2;
p1=p11;
p2=p22;

 while(*p1)
p1++;

 while(*p2)
{
*p1=*p2;
p2++;
p1++;
}
*p1='\0';
}
/*
Enter first string:
Hello India
Enter second string to concatenate to first:
How are you

Conacatenated String is:Hello IndiaHow are you
*/
===================================
//1a. strstr:String search return location
#include<stdio.h>
int strStrLocation(char *str1, char *str2);
int main()
{
char str1[20];
char str2[20];
printf("Enter String1:\n");
gets(str1);
printf("Enter String2:\n");
gets(str2);
int r=0;
r=strStrLocation(str1,str2);
if(r!=-1)printf("found at %d\n",r+1);
else printf("Not found\n");
return 0;
}

int strStrLocation(char *str11, char *str22)
{
char *str1;
char *str2;
str1=str11;
str2=str22;
int location=0;

while(*str11)
{
while(*str1==*str2)
{
str1++;
str2++;
if(*str1=='\0'||*str2=='\0') break;
}
if(*str2=='\0')
break;

str11++; location++;
str1=str11;
str2=str22;
}//first while
if(*str11)
{
printf("%c\n",*str11);
return location;
}
else
return -1;
}
/*
Enter String1:
india
Enter String2:
ind
i
found at 1
-bash-3.2$ ./a.out
Enter String1:
ind
Enter String2:
india
Not found
-bash-3.2$ ./a.out
Enter String1:
india is grt
Enter String2:
grt
g
found at 10

*/
//2a. strcmp: string compare -1,0,1
#include<stdio.h>
int strcompare(char *str1, char *str2);
int main()
{
char str1[20];
char str2[20];
printf("Enter String1:\n");
gets(str1);
printf("Enter String1:\n");
gets(str2);
int r;
r=strcompare(str1,str2);
if(r==0)printf("Equal\n");
else if(r>0)printf("Not Equal:%s comes after %s\n",str1,str2);
else printf("Not Equal:%s comes after %s\n",str2,str1);
return 0;
}

int strcompare(char *str1, char *str2)
{
while(((*str1-*str2)==0) && ( (*str1!='\0')|| (*str2!='\0')))
{
str1++;
str2++;
}
printf("*str1=%d,*str2=%d\n",*str1,*str2);
return(*str1-*str2);
}
/*
-bash-3.2$ ./a.out
Enter String1:
ind
Enter String1:
ind
Equal
-bash-3.2$ ./a.out
Enter String1:
ind
Enter String1:
india
Not Equal:india comes after ind
-bash-3.2$ ./a.out

Enter String1:
india
Enter String1:
ind
Not Equal:india comes after ind
-bash-3.2$ ./a.out
Enter String1:
india
Enter String1:
media
Not Equal:media comes after india
-bash-3.2$ ./a.out
Enter String1:
234
Enter String1:
123
Not Equal:234 comes after 123
-bash-3.2$ ./a.out
Enter String1:
india
Enter String1:
India
Not Equal:india comes after India

*/

//3a. sorting words in array in alphabetical order
#include<stdio.h>
#include<string.h>
int main()
{
char *str[]={
"Gona","Ram","Samy","Banta","Amita"
};
int i,j;
char *t;
for(i=0;i<5;i++)
{
for(j=i+1;j<5;j++)
{
printf("\nstr[i=%d]%s\t",i,str[i]);
printf("str[j=%d]%s\n",j,str[j]);
if( ( strcmp(str[i],str[j]) )>0)
{
t=str[i];
str[i]=str[j];
str[j]=t;
}
}
printf("\nstr[iiiiii=%d]%s\t",i,str[i]);
}
printf("Sorted Names are:\n");
for(i=0;i<5;i++)
{
printf("%s\n",str[i]);
}
return 0;
}

/*
-bash-3.2$ vi strSort.c
-bash-3.2$ ./a.out

str[i=0]Gona str[j=1]Ram

str[i=0]Gona str[j=2]Samy

str[i=0]Gona str[j=3]Banta

str[i=0]Banta str[j=4]Amita

str[iiiiii=0]Amita
str[i=1]Ram str[j=2]Samy

str[i=1]Ram str[j=3]Gona

str[i=1]Gona str[j=4]Banta

str[iiiiii=1]Banta
str[i=2]Samy str[j=3]Ram

str[i=2]Ram str[j=4]Gona

str[iiiiii=2]Gona
str[i=3]Samy str[j=4]Ram

str[iiiiii=3]Ram
str[iiiiii=4]Samy Sorted Names are:
Amita
Banta
Gona
Ram
Samy
*/

//4a. sorting words in array without library function
#include<stdio.h>
#include<string.h>
int main()
{
//below str is static array of char ptrs so must be initialized
char *str[]={
"san","sa",
"santa","santa",
"Amita","Amit",
"zan","xow"
};
int i,j;
char *t;
for(i=0;i<8;i++)
{
for(j=i+1;j<8;j++)
{
printf("\nstr[i=%d]%s\t",i,str[i]);
printf("str[j=%d]%s\n",j,str[j]);
if( ( strCmp(str[i],str[j]) )>0)
{
t=str[i];
str[i]=str[j];
str[j]=t;
}
}
printf("\nstr[iiiiii=%d]%s\t",i,str[i]);
}
printf("Sorted Names are:\n");
for(i=0;i<8;i++)
{
printf("%s\n",str[i]);
}
return 0;
}
int strCmp(char *s1,char *s2)
{
//if(*s1!='\0'&&*s2!='\0') // 2
//{
while( *s1-*s2==0 && (*s1!='\0' || *s2!='\0')) // 3
{
s1++;
s2++;
}
//}
return(*s1-*s2); // 4
}

/*
-bash-3.2$ ./a.out

str[i=0]san str[j=1]sa

str[i=0]sa str[j=2]santa

str[i=0]sa str[j=3]santa

str[i=0]sa str[j=4]Amita

str[i=0]Amita str[j=5]Amit

str[i=0]Amit str[j=6]zan

str[i=0]Amit str[j=7]xow

str[iiiiii=0]Amit
str[i=1]san str[j=2]santa

str[i=1]san str[j=3]santa

str[i=1]san str[j=4]sa

str[i=1]sa str[j=5]Amita

str[i=1]Amita str[j=6]zan

str[i=1]Amita str[j=7]xow

str[iiiiii=1]Amita
str[i=2]santa str[j=3]santa

str[i=2]santa str[j=4]san

str[i=2]san str[j=5]sa

str[i=2]sa str[j=6]zan

str[i=2]sa str[j=7]xow

str[iiiiii=2]sa
str[i=3]santa str[j=4]santa

str[i=3]santa str[j=5]san

str[i=3]san str[j=6]zan

str[i=3]san str[j=7]xow

str[iiiiii=3]san
str[i=4]santa str[j=5]santa

str[i=4]santa str[j=6]zan

str[i=4]santa str[j=7]xow

str[iiiiii=4]santa
str[i=5]santa str[j=6]zan

str[i=5]santa str[j=7]xow

str[iiiiii=5]santa
str[i=6]zan str[j=7]xow

str[iiiiii=6]xow
str[iiiiii=7]zan Sorted Names are:
Amit
Amita
sa
san
santa
santa
xow
zan
*/
//5a. counting number of chars, digits and special character
#include<stdio.h>

int main()
{
int i;
int character=0,digit=0,splchar=0;
char strr[20];

printf("Enter a string:\n");
gets(strr);

char *str=strr;//must

while(*str!='\0')
//for(i=0;i<strlen(strr);i++)
{
printf("%c\n",*str);
if(
( (*str>=65)&&(*str<=91 ))||
( (*str>=97)&&(*str<=123)) )
character++;

else if((*str>=48)&&(*str<=57))
digit++;
else
splchar++;

 str++;
}
printf("Number of chars=%d\n",character);
printf("Number of digits=%d\n",digit);
printf("Number of splchar=%d\n",splchar);
printf("\n");
return 0;
}
/*
imanoj123!@#$$%^&*
m
a
n
o
j
1
2
3
!
@
#
$
$
%
^
&
*
Number of chars=5
Number of digits=3
Number of splchar=9

*/

//6a. counting number of vowels and consonents
#include<stdio.h>

int main()
{
int i;
int vowel=0,conso=0;
char strr[20];

printf("Enter a string:\n");
gets(strr);

char *str=strr;//must

while(*str!='\0')
//for(i=0;i<strlen(strr);i++)
{
printf("%c\n",*str);
if( (*str=='a')||
(*str=='A')||
(*str=='e')||
(*str=='E')||
(*str=='i')||
(*str=='I')||
(*str=='o')||
(*str=='O')||
(*str=='u')||
(*str=='U'))
//printf("Its vowel");
vowel++;

else
conso++;

str++;
}
printf("Number of vowels=%d\n",vowel);
printf("Number of consonents%d\n",conso);
printf("\n");
return 0;
}
/*
Enter a string:
India
I
n
d
i
a
Number of vowels=3
Number of consonents2
*/

//7. Converting lower to upper and vice versa
/*
Easy program just taking care of the Ascii values and and there case.
The differnce between Uppercase character and Lowercase character is 32.
So if the character is in Uppercase we add 32 to change it to Lowercase and similarly we substract 32 from Lowercase character to make it Uppercase character.
*/
#include<stdio.h>

int main()
{
char string[30];
printf("Eneter a string:\n");
gets(string);
printf("u entered: %s\n",string);

char *str;
str=string;

while(*str!='\0')
{
if((*str>=65) && (*str<=91))
{
*str=*str+32;
str++;
}
else
if((*str>=97) && (*str<=123))
{
*str=*str-32;
str++;
}
else
{
printf("Not a character.\n");
break;
}

}
printf("Converted string is: %s\n",string);
return 0;
}
/*

#include<stdio.h>
int main()
{
char str[30];
printf("Eneter a string:\n");
gets(str);
printf("u entered: %s\n",str);

int i;
for(i=0;str[i]!='\0';i++)
{
if((str[i]>=65) && (str[i]<=91))
{
str[i]=str[i]+32;
}
else
if((str[i]>=97) && (str[i]<=123))
{
str[i]=str[i]-32;
}
else
{
printf("Not a character.\n");
break;
}
}
printf("Converted string is: %s\n",str);
return 0;
}
*/
//8. C program to reverse a sentence keeping the words as it is
#include<stdio.h>
void reverse1(char *x);
void reverse2(char *first, char *last);
int main()
{
char sentence[40];
printf("Enter few string:\n");
gets(sentence);
printf("You Entered:%s\n",sentence);
reverse1(sentence);

return 0;
}
void reverse1(char *s)
{
char *temp=s;
char *word=s;

//temp=s;
//word=s;

while(*temp)
{
temp++;
if(*temp=='\0')//then reverse the word
{
reverse2(word,temp-1);
}
else if(*temp==' ')//then reverse the word
{
reverse2(word,temp-1);
word=temp+1;//word after space becomes the new word
}
}
reverse2(s,temp-1);//then reverse the sentence
printf("Reversed String is:%s\n",s);
}
void reverse2(char *firstt, char *lastt)
{
char t;
while(firstt<lastt)
{
t=*firstt;
*firstt=*lastt;
*lastt=t;
firstt++;
lastt--;
}
}
/*Enter few string:
India is Great
You Entered:India is Great
Reversed String is:Great is India

*/

//9. C program to reverse a sentence character wise
#include<stdio.h>
void reverse1(char *x);
void reverse2(char *first, char *last);
int main()
{
char sentence[40];
printf("Enter few string:\n");
gets(sentence);
printf("You Entered:%s\n",sentence);
reverse1(sentence);

return 0;
}
void reverse1(char *s)
{
char *temp;
char *word;

temp=s;
word=s;

while(*temp)
{
temp++;
}
reverse2(s,temp-1);//then reverse the sentence
printf("Reversed String is:%s\n",s);
}

void reverse2(char *firstt, char *lastt)
{
char t;
while(firstt<lastt)
{
t=*firstt;
*firstt=*lastt;
*lastt=t;
firstt++;
lastt--;
}
}
/*
Enter few string:
India is Great
You Entered:India is Great
Reversed String is:taerG si aidnI
*/
//10. C Program to delete duplicate elements in an array
//C code for removing repeated values of an array

 #include<stdio.h>
int main()
{
int a[20],i,j,k,n;

 printf("\nnEnter array size : ");
scanf("%d",&n);

 printf("\nnAccept Numbers : ",n);
for(i=0;i<n;i++)
scanf("%d",&a[i]);
printf("\nnOriginal array is : ");
for(i=0;i<n;i++)
printf(" %d",a[i]);

 printf("\nnUpdated array is  : ");
for(i=0;i<n;i++)
{
   for(j=i+1;j<n;)
   {
      if(a[j]==a[i])
      {
         for(k=j;k<n;k++)
{
             a[k]=a[k+1];
}
          n--;//else array will contain 0 in deleted duplicate value
      }
      else
         j++;
   }
}

 for(i=0;i<n;i++)
    printf("%d \t",a[i]);
printf("\n");
}
/*
array size : 5
Numbers : 22
33
44
44
22
array is :  22 33 44 44 22
array is  : 22         33      44

*/

 //11. C Program to delete duplicate characters in a string/sentence
//C code for removing repeated characters of a string/sentence
#include<stdio.h>
#include<string.h>
int main()
{
char a[200];
int i,j,k,n;

 printf("Enter a few chars and strings:\n");
gets(a);
printf("\nEntered string is :%s \n",a);

 printf("\nUpdated string without repeated characters is\n");
n=strlen(a);
for(i=0;i<n;i++)
{
   for(j=i+1;j<n;)//mind it no icrement
   {
      if(a[j]==a[i])
      {
         for(k=j;k<n;k++)
{
             a[k]=a[k+1];
}
          n--;//else array will contain 0 in deleted duplicate value
      }
      else
         j++;
   }
}

 for(i=0;i<n;i++)
    printf("%c",a[i]);
printf("\n");
}
/*
Enter a few chars and strings:
india is great aa bb cc dd ee ff gg hh ii jj kk

 Entered string is :india is great aa bb cc dd ee ff gg hh ii jj kk

 Updated string without repeated characters is

 inda sgretbcfhjk
*/

 //12. C Program to delete all duplicate words in a sentence
//C code for removing repeated words of among multiple strings
#include <stdio.h>
#include <string.h>
void main()
{
    char a[100], b[20][20];
    int i, j = 0, k = 0, n, m;
    printf("enter a string\n");
    scanf("%[^\n]s", a);
    for (i = 0;a[i] != '\0';i++)
    {
        if (a[i] == ' ')
        {
            b[k][j] = '\0';
            k++;
            j = 0;
        }
        else
        {
            b[k][j] = a[i];
            j++;
        }
    }
    b[k][j] = '\0';
    for (i = 0;i <= k;i++)
    {
        for (j = i + 1;j <= k;j++)
        {
            if (strcmp(b[i], b[j]) == 0)
            {
                for (m = j;m <= k;m++)
                    strcpy(b[m], b[m + 1]);
                k--;
            }
        }
    }
 for (n = 0;n <= k;n++)
    {
        printf("%s ", b[n]);
    }
}
/*
enter a string:
india is great is countrin in india asia great
india is great countrin in asia

*/
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