1.9 KiB
1.9 KiB
Binary Search Algorithm
2022-06-13 15:46
Algorithms:
#algorithm #binary_search
Data structures:
#DS #array #vector #set #multiset
Difficulty:
#CS_analysis #difficulty-easy
Related problems:
tag:#coding_problem tag:#binary_search -tag:#template_remove_me
Links:
How to implement Binary search?
a: Use cpp's library
Use cpp's set's find or equal_range
b: Manual
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Use a while loop: Leetcode Search-a-2D-Matrix#Solution
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Use recursion: from g4g:
// C++ program to implement recursive Binary Search
#include <bits/stdc++.h>
using namespace std;
// A recursive binary search function. It returns
// location of x in given array arr[l..r] is present,
// otherwise -1
int binarySearch(int arr[], int l, int r, int x) {
if (r >= l) {
int mid = l + (r - l) / 2;
// If the element is present at the middle
// itself
if (arr[mid] == x)
return mid;
// If element is smaller than mid, then
// it can only be present in left subarray
if (arr[mid] > x)
return binarySearch(arr, l, mid - 1, x);
// Else the element can only be present
// in right subarray
return binarySearch(arr, mid + 1, r, x);
}
// We reach here when element is not
// present in array
return -1;
}
int main(void) {
int arr[] = {2, 3, 4, 10, 40};
int x = 10;
int n = sizeof(arr) / sizeof(arr[0]);
int result = binarySearch(arr, 0, n - 1, x);
(result == -1) ? cout << "Element is not present in array"
: cout << "Element is present at index " << result;
return 0;
}