stable_sort

Algorithm

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
• Complexity
• Example
• Warnings
• See Also

A templatized algorithm for sorting collections of entities.

None

#include <algorithm>
template <class RandomAccessIterator>
void stable_sort (RandomAccessIterator first, 
                  RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
void stable_sort (RandomAccessIterator first,
                  RandomAccessIterator last, Compare comp);

The stable_sort algorithm sorts the elements in the range [first, last). The first version of the algorithm uses less than (<) as the comparison operator for the sort. The second version uses the comparison function comp.

The stable_sort algorithm is considered stable because the relative order of the equal elements is preserved.

stable_sort does at most N(logN)2 comparisons, where N equals last - first. If enough extra memory is available, it does at most NlogN.

//
// sort.cpp
//
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>
using namespace std;

struct associate
 {
int num;
char chr;

associate(int n, char c) : num(n), chr(c) {};
associate() : num(0), chr(`\0'){};
 };


bool operator<(const associate &x, const associate &y)
 {
return x.num < y.num;
 }


ostream& operator<<(ostream &s, const associate &x)
 {
return s << "<" << x.num << ";" << x.chr << ">";
 }

int main ()
 {
vector<associate>::iterator i, j, k;
associate arr[20] = 
  {associate(-4, ` `), associate(16, ` `),
   associate(17, ` `), associate(-3, `s'),
   associate(14, ` `), associate(-6, ` `),
   associate(-1, ` `), associate(-3, `t'),
   associate(23, ` `), associate(-3, `a'),
   associate(-2, ` `), associate(-7, ` `),
   associate(-3, `b'), associate(-8, ` `),
   associate(11, ` `), associate(-3, `l'),
   associate(15, ` `), associate(-5, ` `),
   associate(-3, `e'), associate(15, ` `)};

// Set up vectors
vector<associate> v(arr, arr+20), v1((size_t)20), 
                  v2((size_t)20);

// Copy original vector to vectors #1 and #2
copy(v.begin(), v.end(), v1.begin());
copy(v.begin(), v.end(), v2.begin());

// Sort vector #1
sort(v1.begin(), v1.end());

// Stable sort vector #2
stable_sort(v2.begin(), v2.end());

// Display the results
cout << "Original    sort      stable_sort" << endl;
for(i = v.begin(), j = v1.begin(), k = v2.begin();
  i != v.end(); i++, j++, k++)
  cout << *i << "     " << *j << "     " << *k << endl;


return 0;
 }

Program Output

Original    sort      stable_sort
<-4; >     <-8; >     <-8; >
<16; >     <-7; >     <-7; >
<17; >     <-6; >     <-6; >
<-3;s>     <-5; >     <-5; >
<14; >     <-4; >     <-4; >
<-6; >     <-3;e>     <-3;s>
<-1; >     <-3;s>     <-3;t>
<-3;t>     <-3;l>     <-3;a>
<23; >     <-3;t>     <-3;b>
<-3;a>     <-3;b>     <-3;l>
<-2; >     <-3;a>     <-3;e>
<-7; >     <-2; >     <-2; >
<-3;b>     <-1; >     <-1; >
<-8; >     <11; >     <11; >
<11; >     <14; >     <14; >
<-3;l>     <15; >     <15; >
<15; >     <15; >     <15; >
<-5; >     <16; >     <16; >
<-3;e>     <17; >     <17; >
<15; >     <23; >     <23; >

If your compiler does not support default template parameters, then you always need to supply the Allocator template argument. For instance, you need to write:

vector<int, allocator>

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.

sort,partial_sort, partial_sort_copy