binary search function in c++
#include <iostream>
using namespace std;
// This program performs a binary search through an array, must be sorted to work
int binarySearch(int array[], int size, int value)
{
int first = 0, // First array element
last = size - 1, // Last array element
middle, // Mid point of search
position = -1; // Position of search value
bool found = false; // Flag
while (!found && first <= last)
{
middle = (first + last) / 2; // Calculate mid point
if (array[middle] == value) // If value is found at mid
{
found = true;
position = middle;
}
else if (array[middle] > value) // If value is in lower half
last = middle - 1;
else
first = middle + 1; // If value is in upper half
}
return position;
}
int main ()
{
const int size = 5; // size initialization
int array[size] = {1, 2, 3, 4, 5}; // declare array of size 10
int value; // declare value to be searched for
int result; // declare variable that will be returned after binary search
cout << "What value would you like to search for? "; // prompt user to enter value
cin >> value;
result = binarySearch(array, size, value);
if (result == -1) // if value isn't found display this message
cout << "Not found\n";
else // If value is found, displays message
cout << "Your value is in the array.\n";
return 0;
}
3.8
5
//requires header <algorithm> for std::binary_search
#include <algorithm>
#include <vector>
bool binarySearchVector(const std::vector<int>& vector,
int target) {
//this line does all binary searching
return std::binary_search(vector.cbegin(), vector.cend(), target);
}
#include <iostream>
int main()
{
std::vector<int> haystack {1, 3, 4, 5, 9};
std::vector<int> needles {1, 2, 3};
for (auto needle : needles) {
std::cout << "Searching for " << needle << std::endl;
if (binarySearchVector(haystack, needle)) {
std::cout << "Found " << needle << std::endl;
} else {
std::cout << "no dice!" << std::endl;
}
}
}
Thank you!
5
0
4.13
8
#include<iostream>
using namespace std;
int binarySearch(int arr[], int p, int r, int num) {
if (p <= r) {
int mid = (p + r)/2;
if (arr[mid] == num)
return mid ;
if (arr[mid] > num)
return binarySearch(arr, p, mid-1, num);
if (arr[mid] > num)
return binarySearch(arr, mid+1, r, num);
}
return -1;
}
int main(void) {
int arr[] = {1, 3, 7, 15, 18, 20, 25, 33, 36, 40};
int n = sizeof(arr)/ sizeof(arr[0]);
int num = 33;
int index = binarySearch (arr, 0, n-1, num);
if(index == -1)
cout<< num <<" is not present in the array";
else
cout<< num <<" is present at index "<< index <<" in the array";
return 0;
}
Thank you!
8
0
4.75
4
#include<iostream>
using namespace std;
int binarySearch(int arr[], int p, int r, int num) {
if (p <= r) {
int mid = (p + r)/2;
if (arr[mid] == num)
return mid ;
if (arr[mid] > num)
return binarySearch(arr, p, mid-1, num);
if (arr[mid] < num)
return binarySearch(arr, mid+1, r, num);
}
return -1;
}
int main(void) {
int arr[] = {1, 3, 7, 15, 18, 20, 25, 33, 36, 40};
int n = sizeof(arr)/ sizeof(arr[0]);
int num = 33;
int index = binarySearch (arr, 0, n-1, num);
if(index == -1)
cout<< num <<" is not present in the array";
else
cout<< num <<" is present at index "<< index <<" in the array";
return 0;
}
Thank you!
4
0
4.5
8
// BY shivam kumar KIIT
#include<bits/stdc++.h>
usind namespace std;
int main()
{
int arr[]={10,2,34,2,5,4,1};
sort(arr,arr+7);//sort array in ascending order before using binary search
binary_search(arr,arr+7,10);//return 1 as element is found
binary_search(arr,arr+7,3);//return 0 as element is not found
return 0;
}
Thank you!
8
0
3.9
10
//By Sudhanshu Sharan
#include<iostream>
#include<cmath>
using namespace std;
// BCT= o(1) and WCT=O(logn) time taken for unsucessful search is always o(logn)
int BinSearch( int arr[],int key,int len)
{
int h,mid,l;
l=0;
h=len-1;
while(l<=h)
{
mid=((l+h)/2);
if(key==arr[mid])
return mid;
else if(key<arr[mid])
h=mid-1;
else
l=mid+1;
}
return -1;
}
int main()
{
int key,i,len;
int arr[] = {1,2,3,6,9,12,15,34,54};
len=sizeof(arr)/sizeof(arr[0]);
cout<<"enter the key to be searched";
cin>>key;
int result= BinSearch(arr,key,len);
(result == -1)
? cout<<"Element is not present in the array"<<endl
: cout<<"Element is present at index : "<<result<<endl;
for(i=0;i<len-1;i++)
cout<<arr[i]<<" ";
return 0;
}
Thank you!
10
0
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