C++ Primer（第5版） 练习 13.40

练习 13.40 为你的StrVec类添加一个构造函数，它接受一个Initializer_list参数。

环境：Linux Ubuntu（云服务器）

工具：vim

 

代码块

/*************************************************************************> File Name: ex13.39.cpp> Author: > Mail: > Created Time: Fri 26 Apr 2024 08:38:31 AM CST************************************************************************/#include<iostream>
#include<memory>
#include<utility>
#include<initializer_list>
using namespace std;class StrVec{public:StrVec(): elements(nullptr), first_free(nullptr), cap(nullptr) {}StrVec(const StrVec &);StrVec(initializer_list<string>li);StrVec &operator= (const StrVec &);~StrVec();void push_back(const string &);size_t size() const { return first_free - elements; } size_t capacity() const { return cap - elements; }string *begin() const { return elements; }string *end() const { return first_free; }void reserve(size_t s);void resize(size_t s);private:Static allocator<string> alloc;void chk_n_alloc(){ if (size() == capacity()) reallocate(); }pair<string*, string*>alloc_n_copy(const string*, const string*);void free();void reallocate();string *elements;string *first_free;string *cap;
};void StrVec::push_back(const string &s){chk_n_alloc();alloc.construct(first_free++, s);
}pair<string*, string*>StrVec::alloc_n_copy(const string *b, const string *e){auto data = alloc.allocate(e - b);return {data, uninitialized_copy(b, e, data)};
}void StrVec:free(){if(elements){for(auto p = first_free; p != elements; ){alloc.destroy(--p);}alloc.deallocate(elements, cap - elements);}
}StrVec::StrVec(const StrVec &s){auto newdata = alloc_n_copy(s.begin(), s.end());elements = newdata.first;first_free = cap = newdata.second;
}StrVec::~StrVec() { free(); }StrVec &StrVec::operator= (const StrVec &rhs){auto data = alloc_n_copy(rhs.begin(), rhs.end());free();elements = data.first;first_free = cap = data.second;return *this;
}void StrVec::reallocate(){auto newcapacity = size() ? 2 * size() : 1;auto newdata = alloc.allocate(newcapacity);auto dest = newdata;auto elem = elements;for(size_t i = 0; i != size(); ++i){alloc.construct(dest++, move(*elem++));}free();elements = newdata;first_free = dest;cap = elements + newcapacity;
}void StrVec::reserve(size_t s){if(s <= size()){return;}auto newElem = alloc.allocate(s);auto dest = newElem;auto elem = elements;for(size_t i = 0; i != size(); ++i){alloc.construct(dest++, move(*elem++));}free();elements = newElem;cap = newElem + s;first_free = dest;
}void StrVec::resize(size_t s){if(s > capacity()){return ;}if(s < size()){auto newFisrt = first_free;for(size_t i = 0; i != size() - s; ++i){alloc.destroy(--newFirst);}fisrt_free = newFirst;return ;}else if(s == size()){return ;}else{auto newFirst = first_free;for(size_t i = 0; i != s - size(); ++i){alloc.construct(newFirst++, "");}first_free = newFirst;return ;}
}