两组之间的差异是由第一组中存在但第二组中没有的元素形成的。函数复制的元素始终以相同的顺序来自第一个范围。
两个范围内的元素都应已订购。
1.使用“ <”比较元素：
句法 ：
Template :
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
Parameters :
first1, last1
Input iterators to the initial and final positions of the first
sorted sequence. The range used is [first1, last1), which contains
all the elements between first1 and last1, including the element
pointed by first1 but not the element pointed by last1.
first2, last2
Input iterators to the initial and final positions of the second
sorted sequence. The range used is [first2, last2).
result
Output iterator to the initial position of the range where the
resulting sequence is stored.
The pointed type shall support being assigned the value of an
element from the first range.
Return Type :
An iterator to the end of the constructed range.
// CPP program to illustrate
// std :: set_difference
#include
int main()
{
int first[] = { 5, 10, 15, 20, 25 };
int second[] = { 50, 40, 30, 20, 10 };
int n = sizeof(first) / sizeof(first[0]);
std::vector v2(5);
std::vector::iterator it, ls;
std::sort(first, first + 5);
std::sort(second, second + 5);
// Print elements
std::cout << "First array :";
for (int i = 0; i < n; i++)
std::cout << " " << first[i];
std::cout << "\n";
// Print elements
std::cout << "Second array :";
for (int i = 0; i < n; i++)
std::cout << " " << second[i];
std::cout << "\n\n";
// using default comparison
/* first array intersection second array */
ls = std::set_difference(first, first + 5, second, second + 5, v2.begin());
std::cout << "Using default comparison, \n";
std::cout << "The difference has " << (ls - v2.begin()) << " elements :";
for (it = v2.begin(); it < ls; ++it)
std::cout << " " << *it;
std::cout << "\n";
return 0;
}
输出：
First array : 5 10 15 20 25
Second array : 10 20 30 40 50
Using default comparison,
The difference has 3 elements : 5 15 25
2.通过使用预定义函数进行比较：
Template :
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
Parameters :
first1, last1, first2, last2, result are same as above.
comp
Binary function that accepts two arguments of the types pointed
by the input iterators, and returns a value convertible to bool.
The function shall not modify any of its arguments.
This can either be a function pointer or a function object.
Return Type :
An iterator to the end of the constructed range.
// CPP program to illustrate
// std :: set_difference
#include
bool comp(int i, int j)
{
return (i < j);
}
int main()
{
int first[] = { 50, 40, 30, 20, 10 };
int second[] = { 5, 10, 15, 20, 25 };
int n = sizeof(first) / sizeof(first[0]);
std::vector v1(5);
std::sort(first, first + 5);
std::sort(second, second + 5);
// Print elements
std::cout << "First array :";
for (int i = 0; i < n; i++)
std::cout << " " << first[i];
std::cout << "\n";
// Print elements
std::cout << "Second array :";
for (int i = 0; i < n; i++)
std::cout << " " << second[i];
std::cout << "\n\n";
// using custom comparison, function as comp
/* first array intersection second array */
ls = std::set_difference(second, second + 5, first, first + 5, v1.begin(), comp);
std::cout << "Using custom comparison, \n";
std::cout << "The difference has " << (ls - v1.begin()) << " elements :";
for (it = v1.begin(); it < ls; ++it)
std::cout << " " << *it;
std::cout << "\n";
return 0;
}
输出：
First array : 10 20 30 40 50
Second array : 5 10 15 20 25
Using custom comparison :
The difference has 3 elements : 30 40 50
可能的应用：用于查找仅在第一个列表中而不在第二个列表中存在的元素。
1.它可用于查找仅参加第一堂课的学生列表。
// CPP program to demonstrate use of
// std :: set_difference
#include
#include
#include
#include
using namespace std;
// Driver code
int main()
{
string first[] = { "Sachin", "Rakesh", "Sandeep", "Serena" };
string second[] = { "Vaibhav", "Sandeep", "Rakesh", "Neha" };
int n = sizeof(first) / sizeof(first[0]);
// Print students of first list
cout << "Students in first class :";
for (int i = 0; i < n; i++)
cout << " " << first[i];
cout << "\n";
// Print students of second list
cout << "Students in second class :";
for (int i = 0; i < n; i++)
cout << " " << second[i];
cout << "\n\n";
vector v(10);
vector::iterator it, st;
// Sorting both the list
sort(first, first + n);
sort(second, second + n);
// Using default operator<
it = set_difference(first, first + n, second, second + n, v.begin());
cout << "Students attending first class only are :\n";
for (st = v.begin(); st != it; ++st)
cout << ' ' << *st;
cout << '\n';
return 0;
}
输出 ：
Students in first class : Sachin Rakesh Sandeep Serena
Students in second class : Vaibhav Sandeep Rakesh Neha
Students attending first classe only are :
Sachin Serena
2.也可以用来查找仅不在第一列表中的元素。
程序在上面给出。
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