C++ Tutorial/vector/Algorithm

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Fill elements in a vector with custom generator

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>

using namespace std; int Fibonacci(void){ 

 static int r;
 static int f1 = 0;
 static int f2 = 1;
 r = f1 + f2;
 f1 = f2;
 f2 = r;
 return f1;

} int main(void){ 

 const int VECTOR_SIZE = 15;
 typedef vector<int> IntVector;
 typedef IntVector::iterator IntVectorIt;
 IntVector Numbers(VECTOR_SIZE);
 IntVectorIt start, end , it;
 int i;
 for(i = 0; i < VECTOR_SIZE; i++)
   Numbers[i] = i * i;
 start = Numbers.begin();
 end = Numbers.end();
 for (it = start; it != end; it++)
   cout << *it << " ";
 generate_n(start + 5, Numbers.size() - 5, Fibonacci);
 for (it = start; it != end; it++)
 cout << *it << " ";

}</source>

find_if, bind2nd and greater_equal

<source lang="cpp">#include <algorithm>

  1. include <vector>
  2. include <iostream>
  3. include <functional>

using namespace std; int main(int argc, char** argv) { 

 int num;
 vector<int> myVector;
 while (true) {
   cout << "Enter a test score to add (0 to stop): ";
   cin >> num;
   if (num == 0) {
     break;
   }
   myVector.push_back(num);
 }
 vector<int>::iterator it = find_if(myVector.begin(), myVector.end(),bind2nd(greater_equal<int>(), 100));
 if (it == myVector.end()) {
   cout << "No perfect scores\n";
 } else {
   cout << "Found a \"perfect\" score of " << *it << endl;
 }
 return (0);

}</source>

Find the first element in the range (first, last + 1) that matches value

<source lang="cpp">#include <iostream>

  1. include <algorithm>

using namespace std ; int main(void) 

{
  const int ARRAY_SIZE = 8;
  int IntArray[ARRAY_SIZE] = { 1, 2, 3, 4, 4, 5, 6, 7 };
  int *location ;  //stores the position of the first matching element.
  int i;
  int value = 4;
  // print content of IntArray
  for (i = 0; i < ARRAY_SIZE; i++)
    cout << IntArray[i] << ", ";
  //Find the first element in the range (first, last + 1) that matches value.
  location = find(IntArray, IntArray + ARRAY_SIZE, value);
  
  //print the matching element if any was found
  if (location != IntArray + ARRAY_SIZE)  
    cout << "First element that matches " << value << " is at location "
    << (location - IntArray) << endl;
  else                    
    cout << "The sequence does not contain any elements with value " << value << endl;

}</source>

for_each element in a vector apply custom function

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>

using namespace std; void PrintCube(int n) { 

   cout << "The cube of " << n << " is " << n * n * n << endl;

} int main(void) { 

   const int VECTOR_SIZE = 8 ;
   typedef vector<int > IntVector ;    
   typedef IntVector::iterator IntVectorIt;
   IntVector Numbers(VECTOR_SIZE) ;    
   IntVectorIt start, end, it ;      
   int i ;
   for (i = 0; i < VECTOR_SIZE; i++)
       Numbers[i] = i + 1 ;
   start = Numbers.begin() ;   
   end = Numbers.end() ;       
   for(it = start; it != end; it++)
       cout << *it << " " ;
   for_each(start, end, PrintCube);

}</source>

Inner product of a vector and another vector

<source lang="cpp">#include <vector>

  1. include <iostream>
  2. include <numeric>

using namespace std; template <class T> void print(T& c){ 

  for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
     std::cout << *i << endl;
  }

} int main() { 

 vector<double> vec1(4, 2.0);  // Length 4, all values == 2.0 
 vector<double> vec2(4, 4.0);  // Length 4, all values == 4.0 
 double init = 0.0; 
 double summation = accumulate (vec1.begin(), vec1.end(), init); 
 cout << "Sum of elements in vector 1: " << summation << endl; 
 double ip = inner_product(vec1.begin(), vec1.end(), vec2.begin(), init); 
 cout << "Inner product of vec1 and vec2: " << ip << endl; 
 int size = 6; 
 int seed_value = 2; 
 vector<int> vec3(size, seed_value); 
 vector<int> result(size); 
 partial_sum(vec3.begin(), vec3.end(), result.begin()); 
 print(result); 
 int sz = 10; 
 int value = 2; 
 vector<int> vec4(sz); 
 vector<int>::iterator it; 
 for (it = vec4.begin(); it != vec4.end(); it++) 
 { 
   (*it) = value; 
   value += 1; 
 } 
 vector<int> result2(vec4.size()); 
 adjacent_difference(vec4.begin(), vec4.end(), result2.begin()); 
 cout << "The adjacent difference of the vector vec4\n"; 
 print(result2); 
 return 0;

}</source>

merge the elements of NumbersVestor and NumbersList and place the results in NumbersDeque

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>
  3. include <list>
  4. include <deque>

using namespace std; int main(void) { 

 const int MAX_ELEMENTS = 8;
 typedef vector<int> IntVector;    
 typedef IntVector::iterator IntVectorIt;
 typedef list<int> IntList;      
 typedef IntList::iterator IntListIt;
 typedef deque<int> IntDeque;    
 typedef IntDeque::iterator IntDequeIt;
 IntVector NumbersVector(MAX_ELEMENTS);
 IntVectorIt startv, endv, itv;
 IntList NumbersList;
 IntListIt first, last, itl;
 IntDeque NumbersDeque(2 * MAX_ELEMENTS);
 IntDequeIt itd;
 NumbersVector[0] = 4;
 NumbersVector[1] = 10;
 NumbersVector[2] = 70;
 NumbersVector[3] = 10;
 NumbersVector[4] = 30;
 NumbersVector[5] = 69;
 NumbersVector[6] = 96;
 NumbersVector[7] = 100;
 first = NumbersList.begin();  
 last = NumbersList.end();    
 //place the results in NumbersDeque
 merge(startv, endv, first, last, NumbersDeque.begin());
 for (itd = NumbersDeque.begin(); itd != NumbersDeque.end(); itd++)
   cout << *itd << " ";

}</source>

Mutating Sequence Algorithm

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>

using namespace std; template<class T> class Print { public: 

    void operator()(const T& t)
    {
        cout << t << " ";
    }

};

int main() { 

    Print<int>    DoPrint;
    vector<int>    vInt(10);

    fill(vInt.begin(), vInt.begin() + 5, 1);
    fill(vInt.begin() + 5, vInt.end(), 2);

    for_each(vInt.begin(), vInt.end(), DoPrint);

    return 0;

}</source>

random number generation in quantitative finance

<source lang="cpp">#include <vector>

  1. include <iostream>
  2. include <algorithm>
  3. include <time.h>

using namespace std; void print(const vector<int>& v) { 

 vector<int>::const_iterator i; 
 cout << "["; 
 for (i=v.begin(); i!=v.end(); i++) cout << *i << ", "; 
 cout << "]" << endl;

} int main() { 

 srand((unsigned) time (NULL)); 
 int Size = 5; 
 vector<int> v1, v2; 
 int i; 
 for (i=0; i<= Size; i++) 
   v1.push_back(rand()); 
 for (i=0; i< Size; i++) 
   v2.push_back(rand()); 
 cout << "Two random lists" << endl; 
 print(v1); 
 print(v2); 
 sort(v1.begin(), v1.end()); 
 sort(v2.begin(), v2.end()); 
 cout << "Two sorted lists" << endl; 
 print(v1); 
 print(v2); 
 // Merge the two lists to a third list 
 vector<int> v3(v1.size()+v2.size()); 
 cout << endl << "Merge the two lists" << endl; 
 merge(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin()); 
 print(v3); 
 return 0;

}</source>

shuffle the elements in a random order

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>

using namespace std; int main(void) { 

   const int VECTOR_SIZE = 8 ;
   typedef vector<int> IntVector ;
   typedef IntVector::iterator IntVectorIt ;
   IntVector Numbers(VECTOR_SIZE) ;
   IntVectorIt start, end, it ;
   Numbers[0] = 4 ;
   Numbers[1] = 10;
   Numbers[2] = 70 ;
   Numbers[3] = 30 ;
   Numbers[4] = 10;
   Numbers[5] = 69 ;
   Numbers[6] = 96 ;
   Numbers[7] = 100;
   start = Numbers.begin() ;   
   end = Numbers.end() ;       
   for(it = start; it != end; it++)
       cout << *it << " " ;
   random_shuffle(start, end) ;
   for(it = start; it != end; it++)
       cout << *it << " " ;

}</source>

The adjacent difference of the vector

<source lang="cpp">#include <vector>

  1. include <iostream>
  2. include <numeric>

using namespace std; template <class T> void print(T& c){ 

  for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
     std::cout << *i << endl;
  }

} int main() { 

 vector<double> vec1(4, 2.0);  // Length 4, all values == 2.0 
 vector<double> vec2(4, 4.0);  // Length 4, all values == 4.0 
 double init = 0.0; 
 double summation = accumulate (vec1.begin(), vec1.end(), init); 
 cout << "Sum of elements in vector 1: " << summation << endl; 
 double ip = inner_product(vec1.begin(), vec1.end(), vec2.begin(), init); 
 cout << "Inner product of vec1 and vec2: " << ip << endl; 
 int size = 6; 
 int seed_value = 2; 
 vector<int> vec3(size, seed_value); 
 vector<int> result(size); 
 partial_sum(vec3.begin(), vec3.end(), result.begin()); 
 print(result); 
 int sz = 10; 
 int value = 2; 
 vector<int> vec4(sz); 
 vector<int>::iterator it; 
 for (it = vec4.begin(); it != vec4.end(); it++) 
 { 
   (*it) = value; 
   value += 1; 
 } 
 vector<int> result2(vec4.size()); 
 adjacent_difference(vec4.begin(), vec4.end(), result2.begin()); 
 cout << "The adjacent difference of the vector vec4\n"; 
 print(result2); 
 return 0;

}</source>

Use count to determine the number of "0"s in the vector

<source lang="cpp">#include <algorithm>

  1. include <vector>
  2. include <iostream>

using namespace std; template <typename elementType> bool IsEven (const elementType& number) { 

   return ((number % 2) == 0);

} int main () { 

   vector <int> v;
   for (int nNum = -9; nNum < 10; ++ nNum)
       v.push_back (nNum);
   vector <int>::const_iterator i;
   for ( i = v.begin (); i != v.end (); ++ i )
       cout << *i << " ";
   cout << v.size () << "" elements" << endl;
   // Use count to determine the number of "0"s in the vector
   size_t nNumZeroes = count (v.begin (),v.end (),0);
   cout << "Number of instances of "0": " << nNumZeroes << endl << endl;
   cout << "Searching for an element of value 3 using find: " << endl;
   return 0;

}</source>

Use the count_if algorithm with the unary predicate IsEven

<source lang="cpp">#include <algorithm>

  1. include <vector>
  2. include <iostream>

using namespace std; template <typename elementType> bool IsEven (const elementType& number) { 

   return ((number % 2) == 0);

} int main () { 

   vector <int> v;
   for (int nNum = -9; nNum < 10; ++ nNum)
       v.push_back (nNum);
   vector <int>::const_iterator i;
   for ( i = v.begin (); i != v.end (); ++ i )
       cout << *i << " ";
   cout << v.size () << "" elements" << endl;
   // Use the count_if algorithm with the unary predicate IsEven:
   size_t nNumEvenElements = count_if (v.begin (),v.end (), IsEven <int> );
   cout << "Number of even elements: " << nNumEvenElements << endl;
   cout << "Number of odd elements: ";
   cout << v.size () - nNumEvenElements << endl;
   return 0;

}</source>

Using the for_each() Algorithm

<source lang="cpp">#include <iostream>

  1. include <vector>
  2. include <algorithm>

using namespace std; template<class T> class Print { public: 

   void operator()(const T& t)
   {
       cout << t << " ";
   }

}; int main() { 

   Print<int>    DoPrint;
   vector<int>    vInt(5);
   for (int i = 0; i < 5; ++i)
       vInt[i] = i * 3;
   cout << "for_each()\n";
   for_each(vInt.begin(), vInt.end(), DoPrint);
   cout << "\n";
   return 0;

}</source>

Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/vector/Algorithm&oldid=2210»