title: Extension of Binary search algo to find the first and last index of the key value to be searched in an array
body: <p>The problem is to extend the binary search algorithm to find all occurrences of a target value in a sorted array in the most efficient way. 
  Concretely speaking, the input of the algorithm is (1) a sorted array of integers, where some numbers may appear more than once, and (2) a target integer to be searched. The output of the algorithm should be a pair of index values, indicating the first and last occurrence of the integer in the array, if it does occur. 
  The source code could be in c#, c, c++.</p>
  
  <p>Also, what is the max and min number of comparisons that we might need to find the indexes?</p>