Question

How would I implement a binary search using just an array?

Answer 1

Ensure that your array is sorted since this is the crux of a binary search.

Any indexed/random-access data structure can be binary searched. So when you say using ‘just an array’, I would say arrays are the most basic/common data structure that a binary search is employed on.

You can do it recursively (easiest) or iteratively. Time complexity of a binary search is O(log N) which is considerably faster than a linear search of checking each element at O(N). Here are some examples from Wikipedia: Binary Search Algorithm:

Recursive:

BinarySearch(A[0..N-1], value, low, high) {       if (high < low)           return -1 // not found       mid = low + ((high - low) / 2)      if (A[mid] > value)           return BinarySearch(A, value, low, mid-1)       else if (A[mid] < value)           return BinarySearch(A, value, mid+1, high)       else        return mid // found     } 

Iterative:

  BinarySearch(A[0..N-1], value) {    low = 0    high = N - 1    while (low <= high) {        mid = low + ((high - low) / 2)        if (A[mid] > value)            high = mid - 1        else if (A[mid] < value)            low = mid + 1        else            return mid // found    }    return -1 // not found }