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