Group all occurrences of characters according to first appearance: C Program

Given a string of lowercase characters, the task is to print the string in a manner such that a character comes first in string displays first with all its occurrences in string.
Examples:

Input :  str = "occurrence"
output : occcurreen 

Input  : str = "cdab"
Output : cdab

C Program

#include <stdio.h>

#include <string.h>

main()

{

char st[100],temp,s[100];

int i,k=0,j,flag=0;

gets(st);

               

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

{

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

                {

                                if(k<strlen(st))

                                {

                                                if(st[i] == st[j])

                                                                s[k++]=st[j];      

                                }

                                else

                                {

                                                flag=1;

                                                break;

                                }                                             

                }

                if(flag ==1)

                                break;

}

s[k]='\0';

puts(s);

}

Remove spaces from string Using Queues: Cprogram

Write a program that compresses a string by deleting all space characters in the string. One way to do so is to use a queue of characters. Insert non space  characters from the string into the queue. When you reach the end of the string , dequeue the characters from the queue and place them back into the string.  

#include <stdio.h>

#define MAX 50

char q[MAX],f=-1,r=-1;

void enq(char val)

{

                if(r == MAX-1)

                                printf("queue is full and hence cannot insert");

                else if(f == -1 && r == -1)

                                f=r=0;

                else

                                r=r+1;

                q[r]=val;

}

char deq()

{

                char val;

                if(f == -1)

                                printf("queue is empty and hence cannot delete");

                else

                {

                                val = q[f];

                                if(f == r)

                                                f=r=-1;

                                else

                                                f=f+1;

                }

                return val;

}

int main()

{

                int i;

                char s[MAX];

                gets(s);

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

                {

                                if(s[i] != ' ')

                                                enq(s[i]);

                }

                for(i= f;i<=r;i++)

                                s[i]=deq();

                s[i]='\0';

                puts(s);

}

Output:

Copying elements of one queue to another queue : C program

#include <stdio.h>

#define MAX 5

int q1[MAX],q2[MAX],f1=-1,r1=-1,f2=-1,r2=-1;

void enq(int q[],int *f,int *r,int val)

{

                if(*r == MAX-1)

                                printf("queue is full and hence cannot insert");

                else if(*f == -1 && *r == -1)

                                *f=*r=0;

                else

                                *r=*r+1;

                q[*r]=val;

}

void display(int q[],int *f, int *r)

{

                int i;

                if(*f == -1)

                                printf("queue is empty ");

                else

                {

                                for(i=*f;i<=*r;i++)

                                                printf("%d\t",q[i]);

                }             

}

main()

{

                int i,val;

                for(i=0;i<MAX;i++)

                {

                                printf("\nenter a value\n");

                                scanf("%d",&val);

                                enq(q1,&f1,&r1,val);

                }

                printf("\nelements in queue 1 are\n");

                display(q1,&f1,&r1);

               

                for(i=f1;i<=r1;i++)

                                enq(q2,&f2,&r2,q1[i]);

                printf("\nelements in queue 2 are\n");

                display(q2,&f2,&r2);

}

Output:

Different AVL Trees for a given set of numbers

 Create any 5 possible AVL trees with the following data  13, 10, 7, 30, 15, 25, 36.