Binary Search Algorithm
Binary search trees keep their keys in sorted order, so that lookup and other operations can use the principle of binary search: when looking for a key in a tree (or a place to insert a new key), they traverse the tree from root to leaf, make comparisons to keys stored in the nodes of the tree and deciding, on the basis of the comparison, to continue searching in the left or right subtrees. They let fast lookup, addition and removal of items, and can be used to implement either dynamic sets of items, or lookup tables that let finding an item by its key (e.g., finding the telephone number of a person by name).
/*
Petar 'PetarV' Velickovic
Algorithm: Binary Search
*/
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <iostream>
#include <vector>
#include <list>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <complex>
#define MAX_N 1000001
using namespace std;
typedef long long lld;
int n, x;
int niz[MAX_N];
//Binarna pretraga elementa u sortiranom nizu
//Slozenost: O(log n)
inline int b_search(int left, int right, int x)
{
int i = left;
int j = right;
while (i < j)
{
int mid = (i+j)/2;
if (niz[mid] == x) return mid;
if (niz[mid] < x) i = mid+1;
else j = mid-1;
}
if (niz[i] == x) return i;
return -1;
}
int main()
{
n = 5, x = 4;
niz[0] = 1;
niz[1] = 2;
niz[2] = 3;
niz[3] = 4;
niz[4] = 5;
printf("%d\n",b_search(0, n-1, x));
return 0;
}
