C ++：从地图的矢量填充经由地图实例分配映射的图(c++ : filling map of map

第2部分我： https://stackoverflow.com/questions/21780627/c-map-of-maps-typedef-doubts-queries

我再向前迈进创造的载体（调整大小） InnerMap ， MiddlMap并执行以下操作：

InnerMap inmap;
vector<InnerMap> vec_inmap;
vec_inmap.resize (8);
int vec_inmap_sz = 8;
vec_inmap.insert (vec_inmap.end (), 8, inmap);
vector<InnerMap>::iterator vec_inmap_it = vec_inmap.begin ();
InnerMap::iterator inmap_it;

MiddlMap mdmap, curr_mdmap;
vector<MiddlMap> vec_mdmap;
vec_mdmap.resize (8);
int vec_mdmap_sz = 8;
vec_mdmap.insert (vec_mdmap.end (), 8, mdmap);
vector<MiddlMap>::iterator vec_mdmap_it = vec_mdmap.begin ();
MiddlMap::iterator mdmap_it;

OuterMap otmap;
OuterMap::iterator otmap_it;

即我存储（空）的副本inmap和mdmap在各自的载体（Q.是它的是，这些拷贝是通过引用？），然后将这些稍后从载体拾取通过相应的向量迭代器，然后相应地填充所述地图。 方法如下：

for (i = 0; i != trainSize; i++) {
...
if (curr_key_otmap != int_key) {
    otmap[int_key] = *vec_mdmap_it;
    vec_mdmap_it++;
    mdmap_count++;
    if (mdmap_count == vec_mdmap_sz) {
        vec_mdmap_sz += 8;
        vec_mdmap.resize (vec_mdmap_sz);
        vec_mdmap.insert (vec_mdmap.end(), 8, mdmap);
    }
    curr_key_otmap = int_key;
    curr_mdmap = otmap[curr_key_otmap];
}

mdmap_it = curr_mdmap.find (int_val);
if (mdmap_it == curr_mdmap.end ()) {
    curr_mdmap[int_val] = *vec_inmap_it;       <--
    curr_mdmap[int_val][char_str] = 1;

    vec_inmap_it++;
    inmap_count++;

    if (inmap_count == vec_inmap_sz) {
        vec_inmap_sz += 8;
        vec_inmap.resize (vec_inmap_sz);
        vec_inmap.insert (vec_inmap.end(), 8, inmap);
    }
} else {
    inmap_it = (*mdmap_it).second.find (char_str);
    if (inmap_it == (*mdmap_it).second.end ()) {
        (*mdmap_it).second[char_str] = 1;
    } else {
        (*mdmap_it).second[char_str] += 1;
    }
}
...
} //for ends

在运行时间过程中..我就到下面的错误<-- ed行：可能有人详细点吗？

Program received signal SIGSEGV, Segmentation fault.
0x0804f9d4 in __gnu_cxx::new_allocator<std::pair<char* const, int> >::construct (this=0xbffff06f, __p=0x8057428, __val=...)
at /usr/include/c++/4.6/ext/new_allocator.h:108
108       { ::new((void *)__p) _Tp(__val); }


#0    0x0804fa2a in __gnu_cxx::new_allocator<std::pair<char* const, int> >::construct (this=0xbffff1bf, __p=0x8057428, __val=...)
at /usr/include/c++/4.6/ext/new_allocator.h:108
#1  0x0804f3e4 in std::_Rb_tree<char*, std::pair<char* const, int>, std::_Select1st<std::pair<char* const, int> >, std::less<char*>, std::allocator<std::pair<char* const, int> > >::_M_create_node (this=0x8098d1c, __x=...) at /usr/include/c++/4.6/bits/stl_tree.h:381
#2  0x0804e25f in std::_Rb_tree<char*, std::pair<char* const, int>, std::_Select1st<std::pair<char* const, int> >, std::less<char*>, std::allocator<std::pair<char* const, int> > >::_M_clone_node (this=0x8098d1c, __x=0xfffffffd) at /usr/include/c++/4.6/bits/stl_tree.h:427
#3  0x0804c645 in std::_Rb_tree<char*, std::pair<char* const, int>, std::_Select1st<std::pair<char* const, int> >, std::less<char*>, std::allocator<std::pair<char* const, int> > >::_M_copy (this=0x8098d1c, __x=0xfffffffd, __p=0x8098d20) at /usr/include/c++/4.6/bits/stl_tree.h:1036
#4  0x0804bda5 in std::_Rb_tree<char*, std::pair<char* const, int>, std::_Select1st<std::pair<char* const, int> >, std::less<char*>, std::allocator<std::pair<char* const, int> > >::operator= (this=0x8098d1c, __x=...) at /usr/include/c++/4.6/bits/stl_tree.h:945
#5  0x0804a714 in std::map<char*, int, std::less<char*>, std::allocator<std::pair<char* const, int> > >::operator= (this=0x8098d1c, __x=...)
at /usr/include/c++/4.6/bits/stl_map.h:255
#6  0x080493ff in MyProg::classify (trainData=..., testsData=...) at my_prog.cpp:83 <-- this is the line I marked
#7  0x08049c72 in main () at my_prog.cpp:200

请让我为编辑/澄清如果有什么是不可破译。

Answer 1:

当调整矢量，除非该空间已经与分配的所有迭代器到矢量变得无效vector::reserve被创建的迭代器前。 这是因为如果有当前分配块之后没有可用存储空间，数据将被复制在其他地方。 如果搬迁情况，对下一次迭代，vec_inmap_it届时将指向可能已被覆盖未分配的内存。 因此，不确定的行为。

// inside for loop
if (mdmap_it == curr_mdmap.end ()) {
    curr_mdmap[int_val] = *vec_inmap_it; // here you dereference vec_inmap_it
    curr_mdmap[int_val][char_str] = 1;

    vec_inmap_it++;
    inmap_count++;

    if (inmap_count == vec_inmap_sz) {
        vec_inmap_sz += 8;
        vec_inmap.resize (vec_inmap_sz); // here you resize the vector, vec_inmap_it is now invalid
        vec_inmap.insert (vec_inmap.end(), 8, inmap);
    }
...

Answer 2:

你知道吗，你的代码是太大了，我不能得到这一切，但我想你应该有这个

 vector<InnerMap*>::iterator vec_inmap_it = vec_inmap.begin ();
 //instead of 
 vector<InnerMap>::iterator vec_inmap_it = vec_inmap.begin ();

试试吧

文章来源: c++ : filling map of maps via map instance allocation from a vector of maps