Flipkart Question: Find fixed point in array

Problem: Given a sorted array of distinct integers, find index i where arr[i] = i. Note that integers in array can be negative. 

Solution: Use binary search to get the index.

Implementation:

int findIndex(int arr[], int low, int high)
{
if(low <= high)
{
int mid = (low + high) / 2;
if(mid == arr[mid])
return mid;
if(mid < arr[mid])
return findIndex(arr, low, mid - 1);
else
return findIndex(arr, mid + 1, high);
}
else
return - 1;
}

Complexity: O(log n)