两组之间的差异由第一组中存在的元素形成，而第二组中不存在。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排序。
1.使用“ <”比较元素：语法：
Template:
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
参数：
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.
返回类型：
An iterator to the end of the constructed range.
// CPP program to illustrate
// std::set_difference
#include <bits/stdc++.h>
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<int> v2(5);
std::vector<int>::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);
参数：
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.
返回类型：
An iterator to the end of the constructed range.
// CPP program to illustrate
// std::set_difference
#include <bits/stdc++.h>
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<int> 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 <iostream>
#include <algorithm>
#include <vector>
#include <string>
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<string> v(10);
vector<string>::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.它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。
相关用法
注：本文由纯净天空筛选整理自 std::set_difference in C++。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。