循环中删除map元素的写法; 在C++环境下,实现一行一行地读入文本文档
14. 循环中删除map元素的写法
typedef map<int,int> mymap;
typedef map<int,int>::iterator myiter;
mymap m; m[1] = 2; m[2] = -1; m[3] = 3; m[4] = 0; m[5] = -5; m[6] = 1;
myiter iter = m.begin();
// for vector, deque
template <class Container, class T>
inline
void vector_erase(Container & c, T const& t)
{
c.erase(std::remove(c.begin(), c.end(), t), c.end());
}
template <class Container, class Pred>
inline
void vector_erase_if(Container & c, Pred pred)
{
c.erase(std::remove_if(c.begin(), c.end(), pred), c.end());
}
// for list, set, map
template <class Container, class T>
void list_erase(Container & c, T const& t)
{
typename Container::iterator
b = c.begin(), e = c.end(), prev = b;
while (b != e)
{
++b;
if (*prev == t) c.erase(prev);
prev = b;
}
}
template <class Container, class Pred>
void list_erase_if(Container & c, Pred pred)
{
typename Container::iterator
b = c.begin(), e = c.end(), prev = b;
while (b != e)
{
++b;
if (pred(*prev)) c.erase(prev);
prev = b;
}
}
template <class Container, class T>
inline
void vector_erase(Container & c, T const& t)
{
c.erase(std::remove(c.begin(), c.end(), t), c.end());
}
template <class Container, class Pred>
inline
void vector_erase_if(Container & c, Pred pred)
{
c.erase(std::remove_if(c.begin(), c.end(), pred), c.end());
}
// for list, set, map
template <class Container, class T>
void list_erase(Container & c, T const& t)
{
typename Container::iterator
b = c.begin(), e = c.end(), prev = b;
while (b != e)
{
++b;
if (*prev == t) c.erase(prev);
prev = b;
}
}
template <class Container, class Pred>
void list_erase_if(Container & c, Pred pred)
{
typename Container::iterator
b = c.begin(), e = c.end(), prev = b;
while (b != e)
{
++b;
if (pred(*prev)) c.erase(prev);
prev = b;
}
}
typedef map<int,int> mymap;
typedef map<int,int>::iterator myiter;
mymap m; m[1] = 2; m[2] = -1; m[3] = 3; m[4] = 0; m[5] = -5; m[6] = 1;
myiter iter = m.begin();
while(iter!=m.end()) {
if(iter->second<0)
m.erase(iter++);
else
++iter;
}
4. 不要用错string.find ,string::find_first_of ,find和find_first_of有本质区别
find是查找子串在string出现的位置
find_first_of是查找第一个匹配目标字符串任何一个字符出现的位置。
(大多数的时候,需要的是find)
15. 从ifstream读出一行到string,使用std::getline(ifstream的成员函数getline做不到)
10. 使用iterator的时候,自增或者自减,多使用++iter ,--iter的格式。
以下代码是在C++环境下,实现一行一行地读入文本文档
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main()
{
ifstream in("your_file");
string line;
while (getline(in,line))
{
cout << line << "\n";
}
return 0;
}
#include <string>
#include <fstream>
using namespace std;
int main()
{
ifstream in("your_file");
string line;
while (getline(in,line))
{
cout << line << "\n";
}
return 0;
}