map.erase()后map.size()的问题
比如有一个map<int,string> 里面有3组数据(1,aaa;2,bbb;3,ccc)
我打算删除掉(2,bbb)这组数据,
可以map.erase(2)吗?还是一定要:
map<int, string>::iterator it;
if(it->first=='2')
map.erase(it);
好像直接erase(2)是可以的,但是map.size()大小好像没有变化......
我猜想:是不是只删除了map的key,但map里面的data和指针仍然存在,才导致size()没有变化?
希望大侠们给小弟解答一下,谢谢!!!
[解决办法]
- C/C++ code
#include <iostream>#include <map>using namespace std;void main() { map<int ,int> m; m[0] = 0; m[10] = 10; m[20] = 20; cout<<m.size()<<endl; m.erase(10); cout<<m.size()<<endl;}
[解决办法]
map erase可以直接用key作参数的。查看一下msdn吧。
[解决办法]
Erase key a.erase(k)
Destroys all elements whose key is the same as k, and removes them from a. [2] The return value is the number of elements that were erased, i.e. the old value of a.count(k).
a.size() is decremented by a.count(k). a contains no elements with key k.