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Occurences_in_sorted_array.c
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Occurences_in_sorted_array.c
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#include<stdio.h>
#include<stdlib.h>
/*
//Brute Force Approach-
int Occurences(int a[] , int n , int item)
{
int count=0;
for(int i=0 ; i<n ;i++)
{
if(a[i] == item)
count++;
}
return count;
}
*/
int firstOccurence(int a[] , int low , int high , int n , int item)
{
if(low <= high)
{
int mid = (low + high)/2;
if((mid == low && a[mid] == item) || (a[mid] == item && a[mid-1] < item))
return mid;
else if(a[mid] >= item)
return firstOccurence(a , low , mid-1 , n , item);
else
return firstOccurence(a , mid+1 , high , n , item);
}
return -1;
}
int lastOccurence(int a[] , int low , int high , int n , int item)
{
if(high >= low)
{
int mid = (low + high)/2;
if((mid == high && a[mid] == item) || (a[mid] == item && a[mid+1] > item))
return mid;
else if(a[mid] <= item)
return lastOccurence(a , mid+1 , high , n , item);
else
return lastOccurence(a , low , mid-1 , n , item);
}
return -1;
}
int main()
{
int n,i,item,index,low,high;
printf("Enter size of array : ");
scanf("%d" , &n);
int a[n];
printf("\nEnter elements of array(sorted order) :\n");
for(i=0 ; i<n ; i++)
scanf("%d" , &a[i]);
printf("\nEnter the element you want to search : ");
scanf("%d",&item);
low = 0 , high = (n-1);
int first = firstOccurence(a , low , high , n , item);
int last = lastOccurence(a , low , high , n , item);
int result = (last - first) + 1;
printf("\nTotal Occurences = %d\n",result);
/*
//Brute Force Approach
int count = Occurences(a , n , item);
printf("\nTotal Occurences = %d\n",count);
*/
return 0;
}