折半查找

最近被人问题，事隔三年了，貌似没什么进步，又写了一遍。

#include <iostream>
#include <string>
using namespace std;

int binary(int array[], int size, int tag);

int main(int argc, char *argv[])
{
  int array[10] = {0, 11, 22, 33, 44, 55, 66, 77, 88, 99};

  cout << binary(array, 10, 0) << endl;
  cout << binary(array, 10, 99) << endl;
  cout << binary(array, 10, 55) << endl;

  cout << binary(array, 10, -23) << endl;
  cout << binary(array, 10, 123) << endl;

  return 0;
}


int binary(int array[], int size,  int tag)
{
  int beg = 0;
  int end = size - 1;
  int pos = 0;

  while (beg <= end)
  {
    pos = (beg + end) / 2;
    if (array[pos] == tag) return pos;

    if (tag > array[pos])
      beg = pos + 1;  //  tag 在右边
    else
      end = pos - 1;  //  tag 在左边
  }

  return -1;
}