Thr problem of the recursive algorithm to do binary search in a sorted array

When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. It allow you to execute lines 1 by 1 and to inspect variables as it execute, it is an incredible learning tool.

Debugger - Wikipedia, the free encyclopedia[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

tl;dr:
you might want to check your test code that calls the Search function - maybe the error is also there!

Long version:

This is not a stand-alone solution, but simply a verification for solution1. I'm only using the solution form for the sake of code formatting:

Using this test code, I could verify that solution 1 is correct:

#include <iostream>
using std::cout;
using std::endl;

int Search(int target, int* start, int* tail){
   if(start>tail){
      cout<<"not find"<<endl;
      return -1;
   }
   int offsetMid= (tail-start)/2/*/sizeof(int)*/;//by unit of int
   cout<<"offset: "<<offsetMid<<"  mid " <<*(start+offsetMid)<<endl;
   cout<<start<<" " <<tail<<endl;
   if(target == *(start+offsetMid) ){
      cout<<"mid"<<endl;
      return (offsetMid+1);
   }
   if(*(start+offsetMid) > target){
      cout<<"left"<<endl;
      tail = start+(offsetMid-1)/**sizeof(int)*/;
      return Search(target, start, tail);
   }
   if(*(start+offsetMid) < target){
      cout<<"right"<<endl;
      start = start+(offsetMid)/**sizeof(int)*/;
      return Search(target,start , tail);
   }
}
void test_Search() {
   int arr[] = {2, 5, 6, 14, 44, 51, 94, 221, 356, 444};
   int* start = arr;
   size_t length = sizeof(arr)/sizeof(int);
   cout << length << endl;
   int *end = start + length;
   int s = Search(6, start, end);
   cout << s << endl;
}

This produces the output:

10
offset: 5  mid 51
0033FA60 0033FA88
left
offset: 2  mid 6
0033FA60 0033FA70
mid
3

Note how in the test function I calculated the end address of the array by explicitely dividing the size of the array by sizeof(int). This is necessary, because adding a number to an int pointer imlpicitely multiplies the address offset by sizeof(int): Suspect that may be the reason why you could not reproduce the expected results when following the advice from solution 1.

P.S.: The compiler complained with the following warning which I did not bother to fix - but you should:

Quote:

warning C4715: 'Search' : not all control paths return a value

It's easy enough to spot, but if you don't, here's a tip: what will happen if you search in the above array for, say, the value 11?