兩組之間的差異由第一組中存在的元素形成，而第二組中不存在。函數複製的元素始終以相同的順序來自第一個範圍。
兩個範圍內的元素都應已排序。
1.使用“ <”比較元素：語法：
Template:
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
參數：
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.
返回類型：
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;
}輸出：
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.通過使用預定義函數進行比較：
Template:
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
參數：
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.
返回類型：
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;
}輸出：
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
可能的應用：用於查找僅在第一個列表中而不在第二個列表中存在的元素。
1.它可用於查找僅參加第一堂課的學生列表。
// 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;
}輸出：
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.它也可以用來查找僅不在第一列表中的元素。程序在上麵給出。
相關用法
注：本文由純淨天空篩選整理自 std::set_difference in C++。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。