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  1.  
  2. // This code is in C++11
  3.  
  4. #include <iostream>
  5. #include <algorithm>
  6. #include <functional>
  7. #include <memory>
  8. #include <climits>
  9. #include <iterator>
  10.  
  11. using namespace std;
  12.  
  13. // :), generic functor
  14. template <typename ArgType, typename ResultType>
  15. struct PredUniqueElements : public std::unary_function<ArgType, ResultType> {
  16.  
  17. public:
  18.     PredUniqueElements(ArgType ref) : prev(ref) {}
  19.  
  20.    ResultType operator() (ArgType curr) {
  21.       ArgType old = prev;
  22.       prev = curr;
  23.       return curr != old;
  24.    }
  25.  
  26. private:
  27.     ArgType prev;
  28. };
  29.  
  30. int GenerateDataSet(int A[], int size) {
  31.     for(int i = 0; i < size; i++)
  32.         A[i] = rand()%size;
  33.  
  34.     sort(A, A+size);
  35.  
  36.     // predicate funtor definition
  37.     PredUniqueElements<int, bool> pred(INT_MIN);
  38.  
  39.     // Retain only unique elements
  40.     auto it = copy_if (A, A+size, A, pred);
  41.     return distance(A, it);
  42. }
  43.  
  44. // Returns location of key, or -1 if not found
  45. int BinarySearchSimple(int A[], int l, int r, int key, int &count)
  46. {
  47.     int m;
  48.  
  49.     while( l <= r )
  50.     {
  51.         m = l + (r-l)/2;
  52.  
  53.         count++;
  54.         if( A[m] == key ) // first comparison
  55.             return m;
  56.  
  57.         count++;
  58.         if( A[m] < key ) // second comparison
  59.             l = m + 1;
  60.         else
  61.             r = m - 1;
  62.     }
  63.  
  64.     return -1;
  65. }
  66.  
  67. int BinarySearch(int A[], int l, int r, int key, int &count)
  68. {
  69.     int m;
  70.  
  71.     while( r - l > 1 )
  72.     {
  73.         m = l + (r-l)/2;
  74.  
  75.         count++;
  76.         if( A[m] <= key )
  77.             l = m;
  78.         else
  79.             r = m;
  80.     }
  81.  
  82.     count++;
  83.     if( A[l] == key )
  84.         return l;
  85.     else
  86.         return -1;
  87. }
  88.  
  89. void TestCase_01() {
  90.     int size = 2048;
  91.     auto_ptr<int> buf(new int[size]);
  92.     int *A = buf.get();
  93.  
  94.     size = GenerateDataSet(A, size);
  95.  
  96.     copy(A, A+size, ostream_iterator<int>(cout, " ")), cout << endl;
  97.  
  98.     int key = 193;
  99.     int count;
  100.  
  101.     // We are only interested in comparison count
  102.     count = 0;
  103.     BinarySearchSimple(A, 0, size-1, key, count);
  104.     cout << "BinarySearchSimple " << count << endl;
  105.  
  106.     count = 0;
  107.     BinarySearch(A, 0, size-1, key, count);
  108.     cout << "BinarySearch " << count << endl;
  109. }
  110.  
  111. int main() {
  112.     srand(unsigned(time(NULL)));
  113.  
  114.     TestCase_01();
  115.  
  116.     return 0;
  117. }
  118.  
Success #stdin #stdout 0s 5320KB
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stdin
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Standard input is empty
stdout
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BinarySearchSimple 20
BinarySearch 12
https://ideone.com/NjdgMa
language:
C++14 (gcc 8.3)
created:
23 hours ago
visibility:
public

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