This document contains code snippets in C programming language for various algorithms and string manipulation functions. Some key snippets include: 1. Code to reverse a string by traversing it from the last index to the first and printing each character. 2. Code implementing the swap algorithm to swap two integers by using a temporary variable. 3. A function to check if a string is a palindrome by comparing the first and last characters in each iteration.

1. String reverse (Important)
#include<stdio.h>
#include<string.h>//Contains strlen , strcat , strtok , strcmp , strupr , strlwr
int main()
{
char str[20];
gets(str);//Getting string
int i;
for(i=strlen(str)-1;i>=0;i--)
{
printf("%c",str[i]);
}
return 0;
}
Input :EIE Department
Output :tnemtrapeD EIE

2. Output :2 5
#include<stdio.h>
int main()
{
int a=5,b=2;
a=a+b;//a=7
b=a-b;//b=5
a=a-b;//a=2
printf("%d %d",a,b);
return 0;
}

3. Input :5
Output :
*
**
***
****
*****
#include<stdio.h>
int main()
{
int n;
scanf("%d",&n);
int i,temp;
for(i=1;i<=n;i++)
{
temp=i;
while(temp--)
{
printf("*");
}
printf("n");
}
return 0;
}

4. #include<stdio.h>
int main()
{
int arr[]={1,2,3,4,5};
int find;
scanf("%d",&find);
int i;
for(i=0;i<5;i++)
{
if(arr[i]==find)
{
printf("%d",i);
return 0;
}
}
return 0;
}
Input :5
Output :4
Frequency is index of an array.

5. #include<stdio.h>
int main()
{
int a,b,i,n,temp;
scanf("%d",&n);
a=0;
b=1;
printf("%d %d ",a,b);
for(i=2;i<n;i++)
{
printf("%d ",a+b);
temp=a+b;
a=b;
b=temp;
}
return 0;
}
Input :5
Output :0 1 1 2 3

6. #include<stdio.h>
#include<math.h>
int result(int num)
{
static int sum=0,i=1;
if(num>0)
{
sum=sum+num%10*i;
i*=2;
num/=10;
result(num);
}
else
return sum;
}
int main()
{
int n;
scanf("%d",&n);
printf("%d",result(n));
return 0;
}
Input :1011001
Output :89

7. #include<stdio.h>
int main()
{
int arr[]={1,6,3,4,9};
int i,j;
for(i=0;i<5;i++)
{
for(j=i+1;j<5;j++)
{
if(arr[i]>arr[j])
{
arr[i]=arr[i]+arr[j];
arr[j]=arr[i]-arr[j];
arr[i]=arr[i]-arr[j];
}
}
}
for(i=0;i<5;i++)
{
printf("%d ",arr[i]);
}
return 0;
}
Output :1 3 4 6 9

8. #include<stdio.h>
#include<string.h>
int main()
{
char str[20];
gets(str);
int i,n=strlen(str),k,j;
for(i=n-1;i>=0;i--)
{
if(str[i]==' ')
{
printf("n");
for(j=i+1;j<n;j++)
{
printf("%c",str[j]);
}
n=i;
continue;
}
if(i==0)
{
printf("n");
strtok(str," ");
printf("%s",str);
}
}
}
Input : I am from India
Output :
India
From
Am
I

9. Strtok(source,destination)
It is used to split a string into two parts.
#include<stdio.h>
#include<string.h>
int main()
{
char str[20];
gets(str);
printf("%s",strtok(str,"-"));// Breaks the string when it finds – in the string
}
Input :EIE-Department
Output :EIE

10. strcmp(string1,string2)
It gives ouput as 0 when both the strings are same
It will give output as -1 when the ASCII value of a character in string2 is greater than
string1
It will give output as 1 when the ASCII value of a character in string1 is greater than
string2
#include<stdio.h>
#include<string.h>
int main()
{
char str1[20],str2[20];
gets(str1);
gets(str2);
printf("%d",strcmp(str1,str2));
}
Str1=Tharun
Str2=Tharun
Output :0

11. strlen(string)
It gives the length of string
#include<stdio.h>
#include<string.h>
int main()
{
char str1[20],str2[20];
gets(str1);
printf("%d",strlen(str1));
}
Input :EIE
Output :3

12. strcat(string1,string2)
It merges the string1 and string2. Stores it in string1.
#include<stdio.h>
#include<string.h>
int main()
{
char str1[20],str2[20];
gets(str1);
gets(str2);
strcat(str1,str2);
printf("%s",str1);
}
Input :
Str1=EIE
Str2=Department
Output :EIEDepartment

13. strcpy(string1,string2)
It copies the string2 and overwrite or paste in string1
#include<stdio.h>
#include<string.h>
int main()
{
char str1[20],str2[20];
gets(str2);
strcpy(str1,str2);
printf("%s",str1);
}
Input :
String2=EIE
Output :EIE

14. #include<stdio.h>
#include<string.h>
int main()
{
char str1[10],str2[10];
gets(str1);
gets(str2);
int i;
for(i=0;i<strlen(str1);i++)
{
if(str1[i]!=str2[i])
{
printf("Not same");
return 0;
}
}
printf("Same");
return 0;
}
Input :
Str1=EIE
Str2=EIE
Output :same

15. #include<stdio.h>
int main()
{
int num;
scanf("%d",&num);
num%2==0?printf("Even"):printf("Odd"); //Conditional operator
return 0;
}
Input :10
Output :Even

16. #include<stdio.h>
int main()
{
int i,j,target;
scanf("%d",&target);
int arr[5];
for(i=0;i<5;i++)
scanf("%d",&arr[i]);
for(i=0;i<5;i++)
{
for(j=1;j<4;j++)
{
if(arr[i]+arr[j]==target)
{
printf("[%d,%d]",arr[i],arr[j]);
}
}
}
}
Input :
5
1 2 3 4 5
Output :
[1,4][2,3][3,2]

17. #include<stdio.h>
int main()
{
int n,i;
scanf("%d",&n);
for(i=2;i<=n/2;i++)
{
if(n%i==0)
{
printf("Not an prime number");
return 0;
}
}
printf("Prime number");
return 0;
}
Input :13
Output :Prime number
Input :12
Output :Not an prime number

18. #include<stdio.h>
int main()
{
int n;
scanf("%d",&n);//n(n+1)/2
printf("%d",n*(n+1)/2);
return 0;
}
Input :8
Output :36
Input :3
Output :6

19. #include<stdio.h>
int main()
{
int n,rem,rev=0;
scanf("%d",&n);
while(n>0)
{
rem=n%10;
rev=rev*10+rem;
n/=10;
}
printf("%d",r);
return 0;
}
Input :12345
Output :54321

20. #include<stdio.h>
int main()
{
int n,num,rem,rev=0;
scanf("%d",&n);
num=n;
while(n>0)
{
rem=n%10;
rev=rev*10+rem;
n/=10;
}
rev==num?printf("Palindrome"):printf("Not
an Palindrome");
return 0;
}
Input :121
Output :Palindrome

21. #include<stdio.h>
#include<math.h>
int length(int number)
{
int len;
while(number>0)
{
number/=10;
len++;
}
return len;
}
int armstrong(int num,int l)
{
int temp=l,result=0;
while(l--)
{
result+=pow(num%10,temp);
num/=10;
}
return result;
}
int main()
{
int n,len,result;
scanf("%d",&n);
len=length(n);
result=armstrong(n,len);
result==n?printf("Armstrong number"):printf("Not
an Armstrong number");
return 0;
}
Input :1634
Output :Armstrong number

22. #include<stdio.h>
int factorial(int number)
{
int i,fact=1;
for(i=1;i<=number;i++)
{
fact*=i;
}
return fact;
}
int result(int n)
{
int sum;
while(n>0)
{
sum+=factorial(n%10);
n/=10;
}
return sum;
}
int main()
{
int n,sum;
scanf("%d",&n);
sum=result(n);
sum==n?printf("strong number"):printf("Not
an strong number");
return 0;
}
Input :145
Output :strong number
Explanation:
1!+4!+5!=145

23. #include<stdio.h>
#include<math.h>
int length(int number)
{
int i;
while(number>0)
{
i++;
number/=10;
}
return i;
}
int main()
{
int n,len;
scanf("%d",&n);
len=length(n);
pow(n,len)==n%pow(10,len)?printf("Automorphic number"):printf("Not an automorphic
number");
return 0;
}
Input :6
Ouput :Automorphic number
Explanation: 6^2=36
6==36%10

24. #include<stdio.h>
int check(int num)
{
int i;
for(i=2;i<=num/2;i++)
{
if(num%i!=0)
continue;
else
return 0;
}
return 1;
}
int main()
{
int n,i,d;
scanf("%d",&n);
for(i=n;i>1;i--)
{
d=check(i);
if(d==0)
continue;
printf("%d",i);
return 0;
}
return 0;
}
Input :100
Output :97

25. #include<stdio.h>
#include<string.h>
int main()
{
char p[15];
gets(p);
int i,j;
for(i=0,j=strlen(p)-1;j>=strlen(p)/2;i++,j--)
if(p[i]!=p[j])
{
printf("Not an palindrome");
return 0;
}
printf("Palindrome");
return 0;
}
Input : abababa
Output : Palindrome