通过迭代器c ++插入元素

Question

我正在尝试将元素插入到集合“教师”中。教师是设置的，这是学校结构的一部分。学校结构在另一个叫做城镇的集合内。我正试图将“格林”老师送入“布朗”担任校长的学校。我用find找到学校，但我无法让他进入。操作符

bool operator<(const School& l, const School& r){
  return (l.headmaster) < (r.headmaster);
}
bool operator==(const School& l, const School& r){
  return (l.headmaster) == (r.headmaster);
}

struct School {
    string headmaster;
    set <string> teachers;
};

set<School>::iterator it;
set <School> town;
// now I alocated few schools and insert them into town, 
School *pSchool = new School(): // i will use pSchool to find school with brown as headmaster
pSchool > headmaster  = "Brown"; // 
it = rozvrh.find(*pSchool);
cout << it->headmaster // gives Brown
it->teachers.insert("Green"); /// error

已编辑..错误

||=== ulohaa1，调试 ===| /home/ulohaa1/main.cpp||在函数'bool transform(const char*, const char*)'中：| /home/ulohaa1/main.cpp|84|错误：没有匹配函数调用‘std::set >::insert(std::string&) const’| /home/michal/Desktop/prog/ulohaa1/main.cpp|84|注意：候选人是：| /usr/include/c++/4.6/bits/stl_set.h|407|注意：std::pair, _Compare, typename _Alloc::rebind<_key>::other>::const_iterator, bool> std::set<_key _compare _alloc>::insert(const value_type&) [with _Key = std::basic_string, _Compare = std::less >, _Alloc = std::allocator >, typename std::_Rb_tree<_key _key std:: _identity>, _Compare, typename _Alloc::rebind<_key>::other>::const_iterator = std::_Rb_tree_const_iterator >, std::set<_key _compare _alloc>::value_type = std::basic_string] | /usr/include/c++/4.6/bits/stl_set.h|407|注意：从 'const std::set >' 到 'std::set >' 的隐式 'this' 参数没有已知的转换>'| /usr/include/c++/4.6/bits/stl_set.h|444|注意：std::set<_key _compare _alloc>::iterator std::set<_key _compare _alloc>::insert(std: :set<_key _compare _alloc>::const_iterator, const value_type&) [with _Key = std::basic_string, _Compare = std::less >, _Alloc = std::allocator >, std::set<_key _compare _alloc>::iterator = std::_Rb_tree_const_iterator >, std::set<_key _compare _alloc>::const_iterator = std::_Rb_tree_const_iterator >, std::set<_key _compare _alloc>::value_type = std: :basic_string]| /usr/include/c++/4.6/bits/stl_set.h|444|注意：候选人需要2个参数，提供1个| /usr/include/c++/4.6/bits/stl_set.h|464|注意：模板 void std::set::insert(_InputIterator, _InputIterator) [with _InputIterator = _InputIterator, _Key = std::basic_string, _Compare = std: :less >, _Alloc = std::allocator >]| ||=== 构建完成：7 个错误，0 个警告 ===|

谢谢你们的帮助

Answer 1

您的编译器错误表明您没有为您的 School 类型重载运算符

#include <set>
#include <string>

struct School
{
    std::string headmaster;
    std::set<std::string> teachers;
    bool operator<(const School& s) const { return headmaster < s.headmaster; }
};

如果你需要更新集合中的一所学校，你需要

1) 在集合中找到学校

2) 如果找到，将值保存到临时学校

3) 更新临时学校

4) 从集合中删除学校并将临时学校插入到集合中

这就是集合容器的本质。更新项目意味着删除和插入更新的项目。所以基本上是这样的：

// we will search for Mr Brown's school and add a teacher
School searchSchool;
searchSchool.headmaster = "Brown";
std::set<School>::iterator it = mainSchool.find(searchSchool);

// if found, add the teacher
if (it != mainSchool.end())
{
    // save the school
    School theSchool = *it;
    theSchool.teachers.insert("A new teacher");
    mainSchool.erase(it);
    mainSchool.insert(theSchool);
}

mainSchool 是您的“全局”集。

编辑：如果使用地图（我认为这是优越的），代码可以像这样简单：

#include <map>
#include <set>
#include <string>
typedef std::set<std::string> StringSet;
typedef std::map<std::string, StringSet>  SchoolMap;

using namespace std;
int main()
{
    SchoolMap allSchools;
    allSchools.insert(make_pair("Brown", StringSet()));
    allSchools.insert(make_pair("Smith", StringSet()));

    // search for Mr Brown's school
    SchoolMap::iterator it = allSchools.find("Brown");

    // if found, add the teacher
    if (it != allSchools.end())
    // save the teacher
        it->second.insert("A new teacher");
}