A C++ STL question - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Programming - 葵花宝典

A C++ STL question

A C++ STL question# Programming - 葵花宝典

T*r2008-02-12 08:02

1 楼

Supposedly I want to delete multiple entries in a STL hash map. The code
looks like the following:
for (it = hash_table.begin(); it != hash_table.end(); it ++)
{
if (some_condition)
hash_table.erase (it);
}
My questions is, after erasing an entry referenced by 'it', will 'it' still
be valid such that you can use 'it++' to find the next entry in the hash map
? Or will 'it' automatically points to the next entry in the hash map
because the total number of entries already reduced by one

p*o2008-02-12 08:02

2 楼

No. You have to compute the next iterator before erasing.

still
map

【在 T********r 的大作中提到】

: Supposedly I want to delete multiple entries in a STL hash map. The code
: looks like the following:
: for (it = hash_table.begin(); it != hash_table.end(); it ++)
: {
: if (some_condition)
: hash_table.erase (it);
: }
: My questions is, after erasing an entry referenced by 'it', will 'it' still
: be valid such that you can use 'it++' to find the next entry in the hash map
: ? Or will 'it' automatically points to the next entry in the hash map

T*B2008-02-12 08:02

3 楼

The iterator is invalidated after the erase operation.

b*n2008-02-12 08:02

4 楼

咱能不能不这麽死心眼啊？
it = hash_table.begin();
while (it != hash_table.end())
{
hash_table::iterator it1 = it+1;
if (some_condition)
hash_table.erase (it);
it = it1;
}

【在 T***B 的大作中提到】

: The iterator is invalidated after the erase operation.

B*e2008-02-12 08:02

5 楼

i think hash_table.erase(it++) should do.
but in this case, you need to adjust for loop to something like:
for (it =..; it != ..; )
{
if ( ...)
hash_table.erase(it++);
else
++it;
}

still
map

【在 T********r 的大作中提到】