cppreference.com > C++ Vectors > Vector operators Vector operators Syntax:
      #include <vector>
      TYPE& operator[]( size_type index );
      const TYPE& operator[]( size_type index ) const;
      vector operator=(const vector& c2);
      bool operator==(const vector& c1, const vector& c2);
      bool operator!=(const vector& c1, const vector& c2);
      bool operator<(const vector& c1, const vector& c2);
      bool operator>(const vector& c1, const vector& c2);
      bool operator<=(const vector& c1, const vector& c2);
      bool operator>=(const vector& c1, const vector& c2);
All of the C++ containers can be compared and assigned with the standard comparison operators: ==, !=, <=, >=, <, >, and =. Individual elements of a vector can be examined with the [] operator. Performing a comparison or assigning one vector to another takes linear time. The [] operator runs in constant time. Two vectors are equal if: Their size is the same, and Each member in location i in one vector is equal to the the member in location i in the other vector. Comparisons among vectors are done lexicographically. For example, the following code uses the [] operator to access all of the elements of a vector:
     vector<int> v( 5, 1 );
     for( int i = 0; i < v.size(); i++ ) {
       cout << "Element " << i << " is " << v[i] << endl;
     }
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