C++ Algorithm reverse()

C++ Algorithm reverse() function is used to reverse the order of the elements within a range [first, last).

Syntax

  template <class BidirectionalIterator>  void reverse (BidirectionalIterator first, BidirectionalIterator last);  

Note: BidirectionalIterator is an iterator which is used to access any elements of a container in both forward and backward direction.

Parameter

first: A bidirectional iterator pointing the position of the first element in the range in which the elements are being reversed.

last: A forward iterator pointing the position one past the final element in the range in which the elements are being reversed.

Return value

None

Complexity

Complexity is linear in the range [first, last): swaps elements.

Data races

The object in the range [first, last) are modified.

Exceptions

This function throws an exception if either an element is swapped or an operation on iterator throws an exception.

Note: The invalid parameters cause an undefined behavior.

Example 1

Let’s see the simple example to reverse the given string:

  #include <algorithm>  #include <iostream>  #include <string>    using namespace std;    int main() {    string str = “Hello Myself Nikita”;    cout << “Before Reverse : “<< str << endl;      reverse(str.begin(), str.end());    cout <<“After Reverse  : ” << str << endl;        return 0;  }  

Output:

Before Reverse : Hello Myself Nikita  After Reverse   : atikiN flesyM olleH

Example 2

Let’s see another simple example to reverse the range of numbers:

  #include <vector>    #include <algorithm>    #include <iostream>      using namespace std;      int main( ) {         vector <int> v1;       vector <int>::iterator Iter1;           int i;       for ( i = 0 ; i <= 9 ; i++ )       {          v1.push_back( i );       }           cout << “The original vector v1 is:n ( ” ;       for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )          cout << *Iter1 << ” “;       cout << “).” << endl;           // Reverse the elements in the vector        reverse (v1.begin( ), v1.end( ) );           cout << “The modified vector v1 with values reversed is:n ( ” ;       for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )          cout << *Iter1 << ” “;       cout << “).” << endl;            return 0;  }    

Output:

The original vector v1 is:   ( 0 1 2 3 4 5 6 7 8 9 ).  The modified vector v1 with values reversed is:   ( 9 8 7 6 5 4 3 2 1 0 ).

Example 3

Let’s see another simple example:

  #include<iostream>   #include<algorithm>   #include<vector>   using namespace std;       int main()   {       vector <int> v ;               // Inserting elements in vector       for (int i = 0; i < 8; i++)           v.push_back(i+10);                 // Displaying elements of vector       vector <int> :: iterator it;       cout<<“Before: “;      for (it = v.begin(); it != v.end(); it++)           cout << (*it) << ” “;               cout << “nnReverse only from index 5 to 7 in array:n”;       // Reversing elements from index 5 to index 7       reverse(v.begin() + 5, v.begin() + 8);               for (it = v.begin(); it != v.end(); it++)           cout << (*it) << ” “;               // Reversing directly from beginning to end       cout << “nReverse full array:n”;               int a[] = {4, 5, 6, 7};       reverse(begin(a), end(a));           // Print the array       cout << a[0] << a[1] << a[2] << a[3] << ‘n’;       return 0;   }   

Output:

Before: 10 11 12 13 14 15 16 17     Reverse only from index 5 to 7 in array:  10 11 12 13 14 17 16 15   Reverse full array:  7654

Example 4

Let’s see another simple example:

  #include <iostream>  #include <algorithm>  #include <vector>  #include <iomanip>  using namespace std;     void print(string a[], int N)  {         for(int i = 0; i < N; i++)      {          cout << (i + 1) << “. ” << setw(5)               << a[i] << ”  “;      }      cout << endl;  }     int main()  {      string s[] = {“George”, “John”, “Nik”, “Alice”, “Bob”, “Watson”};         cout << “Original order : “;      print(s, 6);      cout << “nReversing the order … ” << endl;      reverse(s, s + 6);      cout << “Reversed order : “;      print(s, 6);  }  

Output:

Original order : 1. George  2.  John  3.   Nik  4. Alice  5.   Bob  6. Watson      Reversing the order ....  Reversed order : 1. Watson  2.   Bob  3. Alice  4.   Nik  5.  John  6. George

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C++ algorithm reverse() function

C++ Algorithm reverse()

Syntax

Note: BidirectionalIterator is an iterator which is used to access any elements of a container in both forward and backward direction.

Parameter

Return value

Complexity

Data races

Exceptions

Note: The invalid parameters cause an undefined behavior.

Example 1

Example 2

Example 3

Example 4

Underwriting of Shares

C++ Math abs() Functions

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