Learn First and Follow using a simple example : Compiler Design

Replace Mirror characters in a given string : C program

Given a string and a number N, we need to mirror the characters from N-th position
up to the length of the string in the alphabetical order.
In mirror operation,change ‘a’ to ‘z’, ‘b’ to ‘y’, and so on.

Using the fact that the distance from 'z' to that character and
distance from 'a' to mirror of the character are same.

Program:

#include <stdio.h>

main()

{

char s1[100];

scanf("%[^\n]",s1);

int i,n;

scanf("%d",&n);

for(i=n-1;s1[i]!='\0';i++)

s1[i]='z'-s1[i]+'a';

printf("%s",s1);

}

Output:

section

2

svxgrlm

WAP to Find Highest Frequency Character in a String

#include <stdio.h>

main()

{

char s1[100];

scanf("%[^\n]",s1);

int i,h[26] ={0};

for(i=0;s1[i] != '\0';i++)

h[s1[i] -97 ]++;

int max=0,index;

for(i=0;i<26;i++)

if(h[i]>max)

{

index=i;

max=h[i];

}

printf("%c occured %d times",index+97,max);

}

Array Rotations Questions in C, Arrays: Left Rotation Hacker Rank Solution in C, Circular Array Rotation Hacker Rank Solution in C

Link to Question:
https://www.hackerrank.com/challenges/array-left-rotation/problem
https://www.hackerrank.com/challenges/ctci-array-left-rotation/problem

Program:
#include <stdio.h>

main()

{

 int n,i,d;

 scanf("%d%d",&n,&d);

 int a[n];

 for(i=0;i<n;i++)

  scanf("%d",&a[i]);

  for(i=d;i<d+n;i++)

   printf("%d ",a[i%n]); // we start printing from last index

 }

==============================================================
Circular Array Rotation

Link to Question
https://www.hackerrank.com/challenges/circular-array-rotation/problem

Program

#include <stdio.h>

int main()

{

    int n,i,k,q,j=0;

    scanf("%d%d%d",&n,&k,&q);

    int a[n],b[n];

    for(i=0;i<n;i++)

      scanf("%d",&a[i]);

    //after every n rotations, the rotated array becomes original array

    int r=k%n;

    for(int i=0;i<n;i++)

        b[(i+r)%n]=a[i];

    while(q--)

    {

        int id;

        scanf("%d",&id);

        printf("%d\n",b[id]);

    }

}

You can write the above program without using array b
by using
printf("%d\n",a[(n-(k%n)+m)%n]);

===============================================================================

Just understand the below two programs, you will be able to solve any array rotation problem
output:
5
1 2 3 4 5
2 3 4 5 1
3 4 5 1 2
4 5 1 2 3
5 1 2 3 4
1 2 3 4 5


#include <stdio.h>
main()
{
int n,i,j;
scanf("%d",&n);
int a[n];
for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=1;i<n+1;i++)
{
for(j=i;j<i+n;j++)
printf("%d ",a[j%n]); // we start printing from first index
printf("\n");
}
}

=======================================================================
output:
5
1 2 3 4 5
5 1 2 3 4
4 5 1 2 3
3 4 5 1 2
2 3 4 5 1
1 2 3 4 5

#include <stdio.h>
main()
{
int n,i,j;
scanf("%d",&n);
int a[n];
for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=n-1;i>=0;i--)
{
for(j=i;j<i+n;j++)
printf("%d ",a[j%n]); // we start printing from last index
printf("\n");
}
}

candies hacker rank solution in c

Question: https://www.hackerrank.com/challenges/candies/problem #include <stdio.h> int main() { long int n; scanf("%ld",&n); long int r[n],candies[n],i,sum=0; candies[0]=1; scanf("%ld",&r[i]); for(i=1;i<n;i++) { scanf("%ld",&r[i]); if(r[i]> r[i-1]) candies[i] = candies[i-1]+1; else candies[i] = 1; } sum=candies[n-1]; for(i=n-2;i>=0;i--) { if(r[i]>r[i+1] && candies[i] <= candies[i+1]) candies[i] = candies[i+1]+1; sum=sum+candies[i]; } printf("%ld",sum); }