STL vector中的erase方法（26）

原文地址:http://www.cplusplus.com/reference/vector/vector/erase/

public member function

<vector>

std::vector::erase

• C++98
• C++11

iterator erase (const_iterator position);
iterator erase (const_iterator first, const_iterator last);

Erase elements

Removes from thevectoreither a single element (position) or a range of elements ([first,last)).

从vector中移除单一（position）或者是指定范围内（[first,last））的元素。

指定单一位置例子:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(int argc,char **argv)
{
	vector<int> vi={11,22,33};
	cout<<"vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	auto it=vi.begin();
	vi.erase(it);
	cout<<"after vi.erase(vi.begin()) vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	






}

结果截图:

指定范围例子:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(int argc,char **argv)
{
	vector<int> vi={11,22,33};
	cout<<"vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	auto it=vi.begin();
	vi.erase(it,vi.end());
	cout<<"after vi.erase(vi.begin(),vi.end()) vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	






}

结果截图:

This effectively reduces the containersizeby the number of elements removed, which are destroyed.

这个方法可以高效地删除固定数目的元素，这些元素将被销毁。

Because vectors use an array as their underlying storage, erasing elements in positions other than thevector endcauses the container to relocate all the elements after the segment erased to their new positions. This is generally an inefficient operation compared to the one performed for the same operation by other kinds of sequence containers (such aslistorforward_list).

因为vector底层的存储是采用array，擦除指定位置的元素会造成容器其他的在被擦除后面的元素要重新迁移到新的位置。这通常会导致很大的开销（相对于另一个更好的序列解决方案，例如list,forward_list）。

Parameters

position

Iterator pointing to a single element to be removed from thevector.

Member typesiteratorandconst_iteratorarerandom access iteratortypes that point to elements.

一个指向要被擦除的元素的迭代器。

类型为随机访问迭代器。

first, last

Iterators specifying a range within thevector] to be removed:[first,last). i.e., the range includes all the elements betweenfirstandlast, including the element pointed byfirstbut not the one pointed bylast.

Member typesiteratorandconst_iteratorarerandom access iteratortypes that point to elements。

指示特定范围内将被移除元素位置的迭代器。该范围包括first到last之间的所有元素，包括first指向的元素，但不包括last指向的元素。

Return value

An iterator pointing to the new location of the element that followed the last element erased by the function call. This is thecontainer endif the operation erased the last element in the sequence.

返回值为一个迭代器，其指向被擦除的最后一个元素的下一个位置的元素。

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(int argc,char **argv)
{
	vector<int> vi={11,22,33};
	cout<<"vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	auto it=vi.erase(vi.begin()+1);
	cout<<"after erase(vi.begin()+1) /n return is "<<*it<<endl;

}

截图:

如果被擦除的最后一个元素是整个序列的最后一个元素，那么返回的值为end()迭代器.

Member typeiteratoris arandom access iteratortype that points to elements.

迭代器的类型为随机访问迭代器。

Example

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

// erasing from vector #include <iostream> #include <vector> int main () { std::vector<int> myvector; // set some values (from 1 to 10) for (int i=1; i<=10; i++) myvector.push_back(i); // erase the 6th element myvector.erase (myvector.begin()+5); // erase the first 3 elements: myvector.erase (myvector.begin(),myvector.begin()+3); std::cout << "myvector contains:"; for (unsigned i=0; i<myvector.size(); ++i) std::cout << ' ' << myvector[i]; std::cout << '\n'; return 0; }

Edit & Run

Output:

myvector contains: 4 5 7 8 9 10

Complexity

Linear on the number of elements erased (destructions) plus the number of elements after the last element deleted (moving).

与被擦除元素（析构）的数目加上被擦除元素后面的元素（移动）的数目线性相关。

Iterator validity

Iterators, pointers and references pointing toposition(orfirst) and beyond are invalidated, with all iterators, pointers and references to elements beforeposition(orfirst) are guaranteed to keep referring to the same elements they were referring to before the call.

指向被擦除位置以及其后面位置的迭代器，指针以及引用都将失效，被擦除元素前面的迭代器，指针以及引用依然有效。

Data races

The container is modified.

容器将被修改。

None of the elements beforeposition(orfirst) is accessed, and concurrently accessing or modifying them is safe.

position位置之前的元素不会被访问，同时访问以及修改他们都是安全的。

Exception safety

If the removed elements include the last element in the container, no exceptions are thrown (no-throw guarantee).

如果被擦除的元素包括容器的最后一个元素，不会抛出异常。

Otherwise, the container is guaranteed to end in a valid state (basic guarantee).

An invalidpositionor range causesundefined behavior.

否则，容器只保证最后保持在有效状态。

一个无效的位置或者范围将导致未知的行为。

例子:

<span style="color:#993399;">#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(int argc,char **argv)
{
	vector<int> vi={11,22,33};
	cout<<"vector=";
	for_each(vi.begin(),vi.end(),[](int m){cout<<m<<" ";});
	cout<<endl;
	auto it=vi.erase(vi.end()+1);
	//if(it==vi.end())
	//	cout<<"it==vi.end()"<<endl;
	cout<<"after erase(vi.end()) \n return is "<<*it<<endl;

}</span>

结果截图：

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2014-8-17

于GDUT