迭代器失效小分析

STL中容器按存储方式分为两类：一是按数组容器顺序存储的序列式容器(如：vector, deque) 另一类是以不连续的节点形式存储的容器（list set map）

迭代器失效小实例：

<span style="font-family:Microsoft YaHei;font-size:18px;">void PrintVector(vector<int>& v){vector<int>::iterator it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;}void TestVector(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);vector<int>::iterator it = v.begin();while (it != v.end()){if (*it % 2 == 0)v.erase(it);it++;}}</span>

迭代器失效：对于序列式容器，比如vector删除当前的iterator会使后面所有元素的iteraotr都是小，这是因为顺序容器内存是连续分配，删除一个元素后导致所有的元素会向前移动一个位置.,erase方法可以返回下一个有效的iterator，可以用迭代器接收这个iterator。这样就不会发生迭代器失效的事情了

迭代器失效解决办法：

1.vector实例

<span style="font-family:Microsoft YaHei;font-size:18px;">//迭代器失效void PrintVector(vector<int>& v){vector<int>::iterator it = v.begin();while (it != v.end())//去除偶数{if (*it% 2 == 0)it = v.erase(it);//必须用it接收删除后的下一个迭代器else++it;}it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;} void TestVector(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);PrintVector(v);}</span>

2.list实例

<span style="font-family:Microsoft YaHei;font-size:18px;">void PrintList(list< int>& l1){list<int >::iterator it = l1.begin();for (; it != l1.end(); ++it){cout << *it << " ";}cout << endl;}void Test2(){list<int > l1;l1.push_back(1);l1.push_back(2);l1.push_back(3);l1.push_back(4);l1.push_back(5);l1.push_back(6);l1.push_back(7);l1.push_back(8);PrintList(l1);// 迭代器失效list<int >::iterator it = l1.begin();while (it != l1.end()){if (*it % 2 == 0)it = l1.erase(it);else++it;}PrintList(l1);}</span>