C++ STL中的set::erase用法介绍 _C++开发

set是一种关联容器, 其中每个元素都必须是唯一的, 因为元素的值可以标识它。尽管可以删除并添加该元素的修改后的值, 但是一旦将元素的值添加到集合中就无法对其进行修改。
set::erase()
delete()函数用于从指定位置或范围中删除容器中的元素。
句法：

1. setname.erase(position) 2. setname.erase(startingposition, endingposition) Parameters : Position of the element to be removed in the form of iterator or the range specified using start and end iterator. Result : Elements are removed from the specified position of the container.

例子：

Input: myset{1, 2, 3, 4, 5}, iterator= 2 myset.erase(iterator); Output : 1, 2, 4, 5Input: myset{1, 2, 3, 4, 5, 6, 7, 8}, iterator1= 3, iterator2= 6 myset.erase(iterator1, iterator2); Output : 1, 2, 3, 8

错误和异常
1.如果位置有效, 则没有异常抛出保证。
2.否则显示未定义的行为。
从特定位置移除元件

//INTEGER SET EXAMPLE //CPP program to illustrate //Implementation of erase() function #include < iostream> #include < set> using namespace std; int main() { //set declaration set< int> myset{ 1, 2, 3, 4, 5 }; set< int> ::iterator it1, it2; //defining it1 pointing to the first //element and it2 to the last element it1 = myset.begin(); it2 = myset.end(); //decrementing the it2 two times it2--; it2--; //erasing elements within the range //of it1 and it2 myset.erase(it1, it2); //Printing the set for ( auto it = myset.begin(); it != myset.end(); ++it) cout < < ' ' < < *it; return 0; }

输出如下：

4 5

//CHARACTER SET EXAMPLE //CPP program to illustrate //Implementation of erase() function #include < iostream> #include < set> using namespace std; int main() { //set declaration set< char> myset{ 'A' , 'C' , 'E' , 'G' }; set< char> ::iterator it1, it2; //defining it1 pointing to the first //element and it2 to the last element it1 = myset.begin(); it2 = myset.end(); //decrementing the it2 two times it2--; it2--; //erasing elements within the //range of it1 and it2 myset.erase(it1, it2); //Printing the set for ( auto it = myset.begin(); it != myset.end(); ++it) cout < < ' ' < < *it; return 0; }

输出如下：

E G

删除范围内的元素

//INTEGER SET EXAMPLE //CPP program to illustrate //Implementation of erase() function #include < iostream> #include < set> using namespace std; int main() { //set declaration set< int> myset{ 1, 2, 3, 4, 5 }; set< int> ::iterator it; //defining iterator pointing //to the first element it = myset.begin(); //erasing the first element myset.erase(it); //Printing the set for ( auto it = myset.begin(); it != myset.end(); ++it) cout < < ' ' < < *it; return 0; }

输出如下：

2 3 4 5

//CHARACTER SET EXAMPLE //CPP program to illustrate //Implementation of erase() function #include < iostream> #include < set> using namespace std; int main() { //set declaration set< char> myset{ 'A' , 'B' , 'C' , 'D' }; set< char> ::iterator it; //defining iterator pointing //to the first element it = myset.begin(); //erasing the first element myset.erase(it); //Printing the set for ( auto it = myset.begin(); it != myset.end(); ++it) cout < < ' ' < < *it; return 0; }

输出如下：

B C D

时间复杂度：
1. erase(position)——平摊常量
2. setname.erase(起始位置，结束位置)- O(n)， n是起始位置和结束位置之间的元素数。
应用
给定一组整数, 请从该组中删除所有偶数元素, 然后打印该组。

Input:1, 2, 3, 4, 5, 6, 7, 8, 9 Output :1 3 5 7 9 Explanation - 2, 4, 6 and 8 which are even are erased from the set

算法
1.循环运行直至达到集合的大小。
2.检查每个位置的元素是否可被2整除, 如果是, 则删除该元素, 并将返回迭代器分配给当前迭代器, 如果否, 则将迭代器递增。
3.打印最后一组。
注意：erase返回下一个元素的迭代器

//CPP program to illustrate //Application of erase() function #include < iostream> #include < set> using namespace std; int main() { //set declaration set< int> myset{ 1, 2, 3, 4, 5, 6, 7, 8, 9 }; //checking for even elements and removing them for ( auto i = myset.begin(); i != myset.end(); ) { if (*i % 2 == 0) i=myset.erase(i); else i++; }//Printing the set for ( auto it = myset.begin(); it != myset.end(); ++it) cout < < ' ' < < *it; return 0; }

输出：