79 lines
2.2 KiB
C++
79 lines
2.2 KiB
C++
|
/* Program to demonstrate Indexed sequential search*/
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
#define INTERVAL 5
|
||
|
|
/* If interval is 5 then every 5th element of original array will be represented in index table */
|
||
|
|
|
||
|
|
/* We assume that the original array x is sorted in ascending order */
|
||
|
|
|
||
|
|
struct table
|
||
|
|
{
|
||
|
|
int kindex, pindex ;
|
||
|
|
} ;
|
||
|
|
|
||
|
|
int iss(int x[ ], int n, int key, struct table index[ ], int indexsize) ;
|
||
|
|
|
||
|
|
void main()
|
||
|
|
{
|
||
|
|
/* Size of index table is 1/5th the size of original array since interval is 5 */
|
||
|
|
struct table index[10] ;
|
||
|
|
int i, n, key, indexsize, p, q, x[50] ;
|
||
|
|
clrscr() ;
|
||
|
|
printf("Enter the no of elements: ") ;
|
||
|
|
scanf("%d",&n) ;
|
||
|
|
printf("Enter the elements:\n") ;
|
||
|
|
for(i=0 ; i<n ; i++)
|
||
|
|
scanf("%d",&x[i]) ;
|
||
|
|
/*Creating the index table. p keeps track of original array and q keeps track of index table*/
|
||
|
|
q=0 ;
|
||
|
|
for(p=INTERVAL-1 ; p<n ; p=p+INTERVAL)
|
||
|
|
{
|
||
|
|
index[q].kindex=x[p] ;
|
||
|
|
index[q].pindex=p ;
|
||
|
|
printf("%d %d \n",index[q].kindex,index[q].pindex) ;
|
||
|
|
q++ ;
|
||
|
|
}
|
||
|
|
indexsize=q ;
|
||
|
|
printf("Enter the element to be searched: ") ;
|
||
|
|
scanf("%d",&key) ;
|
||
|
|
i=iss(x,n,key,index,indexsize) ;
|
||
|
|
if(i==-1)
|
||
|
|
printf("%d not found.",key) ;
|
||
|
|
else
|
||
|
|
printf("%d found at position %d.",key,i) ;
|
||
|
|
getch() ;
|
||
|
|
}
|
||
|
|
|
||
|
|
int iss(int x[ ], int n, int key, struct table index[ ], int indexsize)
|
||
|
|
{
|
||
|
|
int i, j, highlimit, lowlimit ;
|
||
|
|
/* Searching the index table */
|
||
|
|
i=0 ;
|
||
|
|
while(i<indexsize)
|
||
|
|
if(index[i].kindex<=key)
|
||
|
|
i++ ;
|
||
|
|
else
|
||
|
|
break ;
|
||
|
|
/* Deciding where searching should start in the original array*/
|
||
|
|
if(i==0)
|
||
|
|
lowlimit=0 ;
|
||
|
|
else
|
||
|
|
lowlimit=index[i-1].pindex ;
|
||
|
|
/* Deciding where searching should end in the original array*/
|
||
|
|
if(i==indexsize)
|
||
|
|
highlimit=n-1 ;
|
||
|
|
else
|
||
|
|
highlimit=index[i].pindex-1 ;
|
||
|
|
/* Searching the original array between lowlimit and highlimit */
|
||
|
|
j=lowlimit ;
|
||
|
|
while(j<=highlimit)
|
||
|
|
if(x[j]!=key)
|
||
|
|
j++ ;
|
||
|
|
else
|
||
|
|
break ;
|
||
|
|
if(j>highlimit)
|
||
|
|
return -1 ;
|
||
|
|
else
|
||
|
|
return j ;
|
||
|
|
}
|