Question

) write a binary search function (using recursion) int binary search(int val, int * a, int first, int last); which searches the values in the sorted array a[] from a[first] to a[last] to find an array element with value val. if it finds val, it returns the position of val in a[]. otherwise it returns -1. for example, given the array a[]

Answer 1

#include <iostream>

#include <algorithm>

int binarySearch(int val, int *a, int first, int last) {

if (first>last) return -1;

int mid = first+(last-first)/2;

if (a[mid]==val) return mid;

// recursive

if (val<a[mid]) return binarySearch(val,a,first,mid-1);

else return binarySearch(val,a,mid+1,last);

}

int main(int argc, char* argv[]) {

int n; std::cin>>n;

int array[n];

for(int i=0;i<n;i++) {

std::cin>>array[i];

}

//Which value?

int v; std::cin>>v;

//Sort before sending the function.

std::sort(array, array+n);

std::cout << "Position: " << binarySearch(v,array,0,n) << std::endl;;

return 0;

}