stl:algorithm:set

set_difference

Syntax:

    #include <algorithm>
    template< typename InIterA, typename InIterB, typename OutIter >
    OutIter set_difference( InIterA start1, InIterA end1, InIterB start2, InIterB end2, OutIter result );
    template< typename InIterA, typename InIterB, typename OutIter, typename StrictWeakOrdering >
    OutIter set_difference( InIterA start1, InIterA end1, InIterB start2, InIterB end2, OutIter result, StrictWeakOrdering cmp );

The set_difference() algorithm computes the difference between two sets defined by [start1,end1) and [start2,end2) and stores the difference starting at result.

Both of the sets, given as ranges, must be sorted in ascending order.

The return value of set_difference() is an iterator to the end of the result range.

If the strict weak ordering comparison function object cmp is not specified, set_difference() will use the < operator to compare elements.

Example

// set_difference example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
 
int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;
 
  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50
 
  it=set_difference (first, first+5, second, second+5, v.begin());
                                               // 5 15 25  0  0  0  0  0  0  0
 
  cout << "difference has " << int(it - v.begin()) << " elements.\n";
 
  return 0;
}

Output: difference has 3 elements