How to delete a value from the nested structure?

Question

Hi Friends!
I have a nested structure such as
multimap<int, map<int ,set<int>>> FinalMul
It contains sample values
1=>4--->1
6=>4--->1
6=>9--->4
11=>4--->1
11=>5--->1   4
11=>9--->4
12=>2--->1   4   5
I want to delete the value 4 from the second and third column,
So, it looks like
1=>
6=>
6=>9--->
11=>
11=>5--->1 
11=>9--->
12=>2--->1  5
after deleting 4, if I have a key(first) (1, 6, 11) and secondkey (second)(6=>9--->,  11=>9--->) with no values, then delete them also.
Finally it looks like
11=>5--->1 
12=>2--->1  5
Can anyone help me how to solve it?
I just tried something;
set<int> tempV;
map<int, set<int>> tempM;
multimap<int, map<int, set<int>>> FinalMul
tempV.insert(1);
tempM.insert(make_pair(4, tempV));
FinalMul.insert(make_pair(1, tempM));
tempV.clear();
tempM.clear();
tempV.insert(1);
tempM.insert(make_pair(4, tempV));
FinalMul.insert(make_pair(6, tempM));
tempV.clear();
tempM.clear();
tempV.insert(4);
tempM.insert(make_pair(9, tempV));
FinalMul.insert(make_pair(6, tempM));
tempV.clear();
tempM.clear();
tempV.insert(1);
tempM.insert(make_pair(4, tempV));
FinalMul.insert(make_pair(11, tempM));
tempV.clear();
tempM.clear();
tempV.insert(1); tempV.insert(4);
tempM.insert(make_pair(5, tempV));
FinalMul.insert(make_pair(11, tempM));
tempV.clear();
tempM.clear();
tempV.insert(4);
tempM.insert(make_pair(9, tempV));
FinalMul.insert(make_pair(11, tempM));
tempV.clear();
tempM.clear();
tempV.insert(1); tempV.insert(4); tempV.insert(5);
tempM.insert(make_pair(2, tempV));
FinalMul.insert(make_pair(12, tempM));

Answer 1

Check this attempt:
typedef
set<int>
SET;
typedef
map<int,
SET>
MAP;
typedef
multimap<int,
MAP>
MULTIMAP;
// remove '4' from second column
for_each( FinalMul.begin(), FinalMul.end(),
[]( MULTIMAP::value_type
& mmv )
MAP & m =
mmv.second;
m.erase( 4 );
// remove '4' from third column and remove empty entries
for_each( FinalMul.begin(), FinalMul.end(),
[]( MULTIMAP::value_type
& mmv )
MAP & m =
mmv.second;
for(
auto i = m.begin(); i != m.end(); )
SET & s = i->second;
s.erase( 4 );
if( s.empty() )
i = m.erase( i );
else
++i;
// remove empty entries
for(
auto i = FinalMul.begin(); i != FinalMul.end(); )
MAP & m = i->second;
if( m.empty() )
i = FinalMul.erase( i );
else
++i;