容器操作--管理迭代器

• 管理迭代器
  –当使用迭代器或指向容器元素的引用时，最小化要求迭代器必须保持有效的程序片段
  –由于向迭代器添加元素时或者删除元素的时候可能会使迭代器失效，因此在容器内做插入删除等操作的时必须重新定位迭代器位置对于vector 、deque、string等线性存储结构尤为重要，但是对于链式存储不影响，他的迭代器，指针和引用都不会失效。
• 如果在一个循环中插入或者删除deque、string、或者vector中的元素，不要缓存end()返回的迭代器。因为会发生变化。迭代器失效。而且这是不好的思路。
• 
  接下来就是代码演示，在代码关键位置会有注释说明。清晰易懂，其中代码不会每行都有注释，代码注释的作用是让读者能够更清晰明了的读懂程序，而不是画蛇添足导致过多的赘述。

#include <iostream>
#include<vector>
#include <list>
#include <forward_list>
#include <stdlib.h>
#include <deque>
#include <string>
using namespace std;
//////////////////////////////////////////////////////////////////////////
//在容器内查找s1,并将s2插入到s1后面
void test_and_insert(forward_list<string>&sflst, const string &s1, const string &s2)
{
    auto prev = sflst.before_begin();
    auto fbengin = sflst.begin();
    bool inserted = false;
    while (fbengin != sflst.end())
        if (*fbengin == s1)
        {
            fbengin = sflst.insert_after(fbengin, s2);
            inserted = true;
        }
        else
        {
            prev = fbengin;
            fbengin++;
        }
    if (!inserted)
    {
        sflst.insert_after(prev, s2);
    }
}
int main(int argc, char **argv)
{
    ////////////////////////Delete member in the contain
    list<int >lst{ 1, 2, 3, 4, 4, 3, 2, 35, 76, 43, 1 };
    auto it = lst.begin();
    while (it != lst.end())
    {
        cout << *it<< " ";
        if (*it % 2)
            it = lst.erase(it);
        else
            ++it;
    }
    it = lst.begin();
    cout << endl;
    while (it != lst.end())
    {
        cout << *it++<< " ";

    }
    cout << endl;//删除容器元素结束；
    //////////////////////////////////////////////////////////////////////////

    int ia[] = { 1, 2, 3, 4, 5, 5, 6, 23, 7, 7 };
    vector<int>iv;
    list<int>il;
    iv.assign(ia, ia + 10);//数据拷贝
    il.assign(ia, ia + 10);


    auto iiv = iv.begin();
    while (iiv != iv.end())
        if (!(*iiv & 1))
            iiv = iv.erase(iiv);
        else
            iiv++;


    auto iil = il.begin();
    while (iil != il.end())
        if (*iil & 1)
            iil = il.erase(iil);
        else
            iil++;
    for (iiv = iv.begin(); iiv != iv.end(); iiv++)
        cout << *iiv << "  ";
    cout << endl;
    for (iil = il.begin(); iil != il.end(); iil++)
        cout << *iil << " ";
    cout << endl;//删除奇偶数
    //////////////////////////////////////////////////////////////////////////
    //forward_list 特殊插入删除操作
    forward_list<int>forlist{ 1, 2, 3, 5, 6, 7, 8, 5, 3, 56, 32, 65, 324, 6 };
    auto prev = forlist.before_begin();
    auto fbegin = forlist.begin();
    while (fbegin != forlist.end())
        if (!(*fbegin % 2))//看是否为偶数或者使用 (!(*fbegin&1))
            fbegin=forlist.erase_after(prev);
        else
        {
            prev = fbegin;
            fbegin++;
        }
    fbegin = forlist.begin();
    while (fbegin != forlist.end())
        cout << *fbegin++ << " ";
    cout << endl;
    //////////////////////////////////////////////////////////////////////////
    //调用函数test_and_insert
    forward_list<string>flist{ "hello", "myheart", "dear", "hai" };
    test_and_insert(flist, "hello", "heihei1");
    auto fllist = flist.begin();
    cout << *(++fllist) << endl;

    //////////////////////////////////////////////////////////////////////////
    //list和forward_list对象的删除和插入操作主要是链式存储
    list<int>ilst{ 23, 45, 2, 3, 21, 45, 23, 234, 433, 5, 6, 76, 4, 2, 2, 5 };
    auto curr = ilst.begin();
    while (curr!=ilst.end())
    {
        if (*curr & 1)
        {
            curr = ilst.insert(curr,*curr);
            curr++;
            curr++;//这里特别注意，要加两次，一次是到插入的元素位置，一次是到下一个

        }
        else
            curr = ilst.erase(curr);
    }
    for (curr = ilst.begin(); curr != ilst.end();curr++)
    {
        cout << *curr << " ";
    }
    cout << endl;
    //////////////////////////////////////////////////////////////////////////
    //vector是如何增长的
    vector<int> words;
    for (int i = 0; i < 258;++i)
    {
        words.push_back(i);
    }
    cout << words.capacity() << " " << words.size() << endl;//316 258
    cout << words.capacity() -words.size() << endl;//58
    words={};
    for (int i = 0; i <258; ++i)
    {
        words.push_back(i);
    }
    cout << words.capacity() << " " << words.size() << endl;//316 258
    cout << words.capacity() - words.size() << endl;//58
    for (int i = 0; i < 258; ++i)
    {
        words.push_back(i);
    }
    cout << words.capacity() << " " << words.size() << endl;//711 517
    cout << words.capacity()- words.size() << endl;//194
    for (int i = 0; i <258; ++i)
    {
        words.push_back(i);
    }
    cout << words.capacity() << " " << words.size() << endl;//1066 775
    cout << words.capacity()-words.size() << endl;//291
    //总结是成倍线性增长的空间，但是也会有些许误差
    system("pause");

}