C++ Programming Code Examples
C++ > Sorting Searching Code Examples
Program to Perform Uniform Binary Search
/* Program to Perform Uniform Binary Search
- Implement binary search using a lookup table.
- It is an improvement in binary search since table lookup is faster than a shift and addition.
- The time complexity is O(log(n)).
- Implement the binary search on a sorted array.
- For the mid index value of any of the sub-array, instead of calculating refer lookup table.
- Exit.
C++ program to implement Uniform Binary Search. */
#include<iostream>
using namespace std;
// A function to create lookup array.
void MakeDelta(int *delta, int N)
{
int power = 1, i = 0;
do
{
int half = power;
power *= 2;
delta[i] = (N+half)/power;
i++;
}while (delta[i-1] != 0);
}
// A function implementing Uniform Binary search.
int UniBinarySearch(int *a, int *del, int key)
{
int i = del[0]-1, d = 0;
flag:
// If item found at mid index return to main.
if (key == a[i])
return i;
// If lookup table vlaue is 0 then no more sub-part of array remain to search hence element not found.
else if (del[d] == 0)
return -1;
else
{
// Shift to left subpart using lookup array 'del'.
if (key < a[i])
{
i -= del[++d];
goto flag;
}
// Shift to right subpart using lookup array 'del'.
else
{
i += del[++d];
goto flag;
}
}
}
int main(void)
{
int i, n = 20,d = 0, pow = 1, index;
char ch;
int a[20] = {1, 8, 4, 9, 13, 18, 19, 22, 24, 36, 77, 48, 43, 96, 88, 79, 83, 92, 94, 99};
// Determine the size of delta array.
while(pow <= n)
{
pow *=2;
d++;
}
int del[d];
// Create lookup array.
MakeDelta(del, n);
up:
cout<<"\nEnter the Element to be searched: ";
cin>>n;
// Implement Uniform Binary search and get index value.
index = UniBinarySearch(a, del, n);
if(index == -1)
cout<<"\nItem not found";
else
cout<<"\nItem "<<n<<" found at "<<index+1<<" position";
// Ask user to enter choice for further searching.
cout<<"\n\n\tDo you want to search more...enter choice(y/n)?";
cin>>ch;
if(ch == 'y' || ch == 'Y')
goto up;
return 0;
}
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