STL算法（集合计算）

简介

set_union
set_intersection
set_difference

set_union取并集

构造一个有序序列，包含两个有序序列的并集。

        // TEMPLATE FUNCTION set_union
template inline
    _OutIt set_union(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
    {   // OR sets [_First1, _Last1) and [_First2, _Last2), using operator<
    return (_STD set_union(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }

 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
template inline
    _OutTy *set_union(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2, _OutTy (&_Dest)[_OutSize])
    {   // OR sets [_First1, _Last1) and [_First2, _Last2), array dest
    return (_STD set_union(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }
 #endif /* _ITERATOR_DEBUG_ARRAY_OVERLOADS */

set_intersection

构造一个有序序列，包含两个有序序列的交集。

        // TEMPLATE FUNCTION set_intersection
template inline
    _OutIt set_intersection(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2, _OutIt _Dest)
    {   // AND sets [_First1, _Last1) and [_First2, _Last2), using operator<
    return (_STD set_intersection(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }

 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
template inline
    _OutTy *set_intersection(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2, _OutTy (&_Dest)[_OutSize])
    {   // AND sets [_First1, _Last1) and [_First2, _Last2), array dest
    return (_STD set_intersection(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }
 #endif /* _ITERATOR_DEBUG_ARRAY_OVERLOADS */

set_difference

构造一个有序序列，该序列保留第一个有序序列中存在而第二个有序序列中不存在的元素。

        // TEMPLATE FUNCTION set_difference
template inline
    _OutIt set_difference(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2,
        _OutIt _Dest)
    {   // take set [_First2, _Last2) from [_First1, _Last1), using operator<
    return (_STD set_difference(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }

 #if _ITERATOR_DEBUG_ARRAY_OVERLOADS
template inline
    _OutTy *set_difference(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _InIt2 _Last2,
        _OutTy (&_Dest)[_OutSize])
    {   // take set [_First2, _Last2) from [_First1, _Last1), array dest
    return (_STD set_difference(_First1, _Last1, _First2, _Last2, _Dest,
        less<>()));
    }
 #endif /* _ITERATOR_DEBUG_ARRAY_OVERLOADS */

注意

• 集合必须有序
• 目的集合的大小要提前分配
• 自定义类型需要重载<操作符

示例

#include "stdafx.h"
#include "stdafx.h"
#include "iostream"
#include "string"
#include "algorithm"
#include "vector"
#include "list"
#include 
#include
using namespace std;
class Student {
private:
    int number;
    string name;
public:
    Student() {
        this->number = 0;
        this->name = "";
    }
    Student(int number, string name) {
        cout << "构造 " << number << " " << name.c_str() << endl;
        this->number = number;
        this->name = name;
    }
    Student(const Student & stu) {
        //cout << "copy构造" <number = stu.getNumber();
        this->name = stu.getName();
    }
    ~Student() {
        //cout<<"析构 " << this->number << " " << this->name.c_str() << endl;
    }

    Student& operator=(const Student& stu) {
        this->number = stu.getNumber();
        this->name = stu.getName();
        return *this;
    }

    void print()const {
        cout << "print 》》 " << this->number << " " << this->name.c_str() << endl;
    }

    int getNumber() const {
        return this->number;
    }
    string getName()const {
        return this->name;
    }

    // 小于运算符用于集合运算  
    bool operator<(const Student &stu) const
    {
        return this->getNumber() < stu.getNumber();
    }
};

void printStuV(vector v) {
    cout << "开始遍历vector============" << endl;
    for (vector::iterator it = v.begin(); it != v.end(); it++) {
        it->print();
    }
    cout << "结束遍历vector============" << endl;
}
void printNum(vectorv) {
    cout << "开始遍历vector============" << endl;
    for (vector::iterator it = v.begin(); it != v.end(); it++) {
        cout << *it << " ";
    }
    cout << endl;
    cout << "结束遍历vector============" << endl;
}

struct ReplaceFunc
{
    bool operator()(const Student & stu1) const {
        cout << "ReplaceFunc》》" << endl;
        return stu1.getNumber() >3;
    }
};

int main()
{
    //accumulate示例，需要include
    vector vNum;
    vNum.push_back(1);
    vNum.push_back(2);
    vNum.push_back(3);
    vector vNum2;
    vNum2.push_back(2);
    vNum2.push_back(3);
    vNum2.push_back(5);
    vector vNum3;
    vNum3.resize(10);
    //取并集
    set_union(vNum.begin(),vNum.end(),vNum2.begin(),vNum2.end(),vNum3.begin());
    printNum(vNum3);
    fill(vNum3.begin(), vNum3.end(), 0);
    //交集
    set_intersection(vNum.begin(), vNum.end(), vNum2.begin(), vNum2.end(), vNum3.begin());
    printNum(vNum3);
    fill(vNum3.begin(), vNum3.end(), 0);
    //差集
    set_difference(vNum.begin(), vNum.end(), vNum2.begin(), vNum2.end(), vNum3.begin());
        printNum(vNum3);
    fill(vNum3.begin(), vNum3.end(), 0);


    cout << endl;
    //将输入值赋给标志范围内的所有元素。
    vector vStu;
    vector vStu2;
    vector vStu3;
    vStu3.resize(10);
    vStu.push_back(Student(1, "one"));
    vStu.push_back(Student(2, "two"));
    vStu.push_back(Student(3, "three"));
    vStu2.push_back(Student(3, "three_2"));
    vStu2.push_back(Student(4, "four"));
    //需要重载<操作符
    set_union(vStu.begin(), vStu.end(), vStu2.begin(), vStu2.end(), vStu3.begin());
    printStuV(vStu3);
}

结果：

jihe.png