If the array contains duplicate elements, which index will binary search return for the key?

Binary search is an algorithm used for finding the position of a target value within a sorted array. It compares the target value to the middle element of the array; if they are unequal, the half in which the target cannot lie is eliminated and the search continues on the remaining half, again taking the middle element to compare to the target value, and repeating this until the target value is found. If the search ends with the remaining half being empty, the target is not in the array.

In the case of an array with duplicate elements, the index that binary search returns can vary. This is because binary search does not necessarily return the first occurrence of the target value in the array. It returns the position of some occurrence of the target value, which could be any of the duplicates depending on how the search proceeds.

For example, consider the sorted array [1, 2, 2, 2, 3, 4, 5] and we want to find the index of 2. The binary search could return the index of any of the three 2's in the array, depending on the exact path the search takes.

If you want to ensure that you always get the first occurrence of the target value, you would need to modify the binary search algorithm to keep track