C++ Tutorial/vector/vector erase

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Erase adjacent duplicates

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

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

using namespace std; typedef vector <string> VECTOR_STRINGS; int main (){

   VECTOR_STRINGS v;
   v.push_back ("A");
   v.push_back ("B");
   v.push_back ("C");
   v.push_back ("D");
   // insert a duplicate into the vector
   v.push_back ("D");
   VECTOR_STRINGS::iterator i;
   // Erase adjacent duplicates
   i = unique (v.begin (), v.end ());
   v.erase (i, v.end ());
   for (size_t nItem = 0; nItem < v.size (); ++ nItem){
       cout << "Name [" << nItem << "] = \"";
       cout << v [nItem] << "\"" << endl;
   }
   return 0;

}</source>

Erase all value in a vector more than three standard deviations greater than the mean

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

  1. include <cmath>
  2. include <functional>
  3. include <iostream>
  4. include <list>
  5. include <numeric>
  6. include <vector>

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( ) {

  const float a[] = { 1, 1.3, 1.5, 0.9, 0.1, 0.2};
  vector<float> data( a,a + sizeof( a ) / sizeof( a[0] ) );
  print( data  );
  float mean = accumulate( data.begin(), data.end(), 0.0f )/ data.size();
  vector<float> zero_mean( data );
  transform( zero_mean.begin(), zero_mean.end(), zero_mean.begin(),bind2nd( minus<float>(), mean ) );
  // compute the sample standard deviation
  float deviation = inner_product( zero_mean.begin(),zero_mean.end(), zero_mean.begin(), 0.0f );
  deviation = sqrt( deviation / ( data.size() - 1 ) );
  // erase all points more than three standard deviations greater than the mean
  const int num_deviations = 3;
  vector<float>::iterator end = remove_if( data.begin(), data.end(), bind2nd( greater<float>(),mean + num_deviations * deviation ) );
  data.erase( end, data.end() );

}</source>

Erase all value in a vector more than three standard deviations less than the mean with erase() remove_if() and bind2nd

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

  1. include <cmath>
  2. include <functional>
  3. include <iostream>
  4. include <list>
  5. include <numeric>
  6. include <vector>

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( ) {

  const float a[] = { 1, 1.3, 1.5, 0.9, 0.1, 0.2};
  // create and initialize vector with above data
  vector<float> data( a,a + sizeof( a ) / sizeof( a[0] ) );
  cout << "DATA VECTOR HAS " << data.size() << " ELEMENTS\n";
  print( data  );
  // compute the mean
  float mean = accumulate( data.begin(), data.end(), 0.0f )/ data.size();
  // subtract the mean from every data point
  vector<float> zero_mean( data );
  transform( zero_mean.begin(), zero_mean.end(), zero_mean.begin(),bind2nd( minus<float>(), mean ) );
  // compute the sample standard deviation
  float deviation = inner_product( zero_mean.begin(),zero_mean.end(), zero_mean.begin(), 0.0f );
  deviation = sqrt( deviation / ( data.size() - 1 ) );
  const int num_deviations = 3;
  // erase all points more than three standard deviations less than the mean
  data.erase( remove_if( data.begin(), data.end(),bind2nd( less<float>(), mean - num_deviations * deviation ) ),data.end() );

}</source>

Erase first element

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

  1. include <vector> // vector class-template definition
  2. include <algorithm> // copy algorithm
  3. include <iterator> // ostream_iterator iterator
  4. include <stdexcept> // out_of_range exception

int main() {

  int array[ 6 ] = { 1, 2, 3, 4, 5, 6 };
  std::vector< int > integers( array, array + 6 );
  std::ostream_iterator< int > output( cout, " " );
  integers.push_back( 2 );
  integers.push_back( 3 );
  integers.push_back( 4 );
  cout << "Vector integers contains: ";
  std::copy( integers.begin(), integers.end(), output );
  // erase first element
  integers.erase( integers.begin() );
  cout << "\n\nVector integers after erasing first element: ";
  std::copy( integers.begin(), integers.end(), output );
  return 0;

}</source>

Vector integers contains: 1 2 3 4 5 6 2 3 4
Vector integers after erasing first element: 2 3 4 5 6 2 3 4

erase the numbers 2 through 5 in v1

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

  1. include <algorithm>
  2. include <iterator>
  3. include <iostream>

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

 copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
 cout << endl;

} int main(int argc, char** argv){

 vector<int> v1, v2;
 int i;
 v1.push_back(1);
 v1.push_back(2);
 v1.push_back(3);
 v1.push_back(5);
 v1.insert(v1.begin() + 3, 4);
 // Add elements 6 through 10 to v2
 for (i = 6; i <= 10; i++) {
   v2.push_back(i);
 }
 printVector(v1);
 printVector(v2);
 // add all the elements from v2 to the end of v1
 v1.insert(v1.end(), v2.begin(), v2.end());
 printVector(v1);
 // erase the numbers 2 through 5 in v1
 v1.erase(v1.begin() + 1, v1.begin() + 5);
 printVector(v1);
 printVector(v2);
 return (0);

}</source>

insert and erase.

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

  1. include <vector>

using namespace std;

int main() {

 vector<char> v(10);
 vector<char> v2;
 char str[] = "<Vector>";
 unsigned int i;
  
 for(i=0; i<10; i++) v[i] = i + "a";
  
 // copy characters in str into v2
 for(i=0; str[i]; i++) 
    v2.push_back(str[i]);

 // display original contents of vector
 cout << "Original contents of v:\n";
 for(i=0; i<v.size(); i++) cout << v[i] << " ";
 cout << "\n\n";
  
 vector<char>::iterator p = v.begin();
 p += 2; // point to 3rd element
  
 // insert 10 X"s into v
 v.insert(p, 10, "X");
  
 // display contents after insertion
 cout << "Size after inserting X"s = " << v.size() << endl;
 cout << "Contents after insert:\n";
 for(i=0; i<v.size(); i++) cout << v[i] << " ";
 cout << "\n\n";
  
 // remove those elements
 p = v.begin();
 p += 2; // point to 3rd element
 v.erase(p, p+10); // remove next 10 elements
  
 // display contents after deletion
 cout << "Size after erase = " << v.size() << endl;
 cout << "Contents after erase:\n";
 for(i=0; i<v.size(); i++) cout << v[i] << " ";
 cout << "\n\n";
  
 // Insert v2 into v
 v.insert(p, v2.begin(), v2.end());
 cout << "Size after v2"s insertion = ";
 cout << v.size() << endl;
 cout << "Contents after insert:\n";
 for(i=0; i<v.size(); i++) cout << v[i] << " ";
 cout << endl;
  
 return 0;

}</source>

Remove(delete) all elements in the vector

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

  1. include <vector> // vector class-template definition
  2. include <algorithm> // copy algorithm
  3. include <iterator> // ostream_iterator iterator
  4. include <stdexcept> // out_of_range exception

int main() {

  int array[ 6 ] = { 1, 2, 3, 4, 5, 6 };
  std::vector< int > integers( array, array + 6 );
  std::ostream_iterator< int > output( cout, " " );
  integers.push_back( 2 );
  integers.push_back( 3 );
  integers.push_back( 4 );
  cout << "Vector integers contains: ";
  std::copy( integers.begin(), integers.end(), output );
  // erase remaining elements
  integers.erase( integers.begin(), integers.end() );
  cout << "\nAfter erasing all elements, vector integers "
     << ( integers.empty() ? "is" : "is not" ) << " empty";
  return 0;

}</source>

Vector integers contains: 1 2 3 4 5 6 2 3 4
After erasing all elements, vector integers is empty

Use unique_copy to remove duplicate words

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
  1. include <iostream>
  2. include <vector>
  3. include <string>
  4. include <algorithm>
  5. include <iterator>

using namespace std; int main() {

   vector<string> coll;
   /* read all words from the standard input
    * - source: all strings until end-of-file (or error)
    * - destination: coll (inserting)
    */
   copy (istream_iterator<string>(cin),    // start of source
         istream_iterator<string>(),       // end of source
         back_inserter(coll));             // destination
   // sort elements
   sort (coll.begin(), coll.end());
   /* print all elements without duplicates
    * - source: coll
    * - destination: standard output (with newline between elements)
    */
   unique_copy (coll.begin(), coll.end(),             // source
                ostream_iterator<string>(cout,"\n")); // destination

}</source>

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