Unordered_map iterator throwing error

Question

I have this code:

int solution(int K, const vector<int> &A) {
  int count=0,size,comp=0;
  unordered_map<long,long> map;

  size = A.size();
  if(size==0)
      return 0;

  for(int i=0;i<size;i++){
      map[A[i]] = i;
  }

  for(int i=0;i<size;i++){
      comp = K-A[i];
      unordered_map<long,long>::const_iterator index = map.find(comp); //error here
      if(index == map.end())
          continue;
      else{
          count++;
      }
  }
  cout << "final count: " << count << endl;
  return count;    
}

I'm getting an error for invalid operands and am unable to figure out what I'm doing wrong. I've tried switching iterators but it also might be my compiler. I'm using this to compile:

clang++ -stdlib=libc++ -std=gnu++11 workingpairs.cpp

My errors are: expected ';' at end of declaration unordered_map::const_iterator index = map.find(comp);

indirection requires pointer operand ('int' invalid) __table_.__insert_unique(*__first);

in instantiation of function template specialization 'std::__1::unordered_map, std::__1::equal_to, std::__1::allocator > >::insert' requested here

Any insight/help would be appreciated!

EDIT:

I've gone back and fixed the error.

This would be a good place to use auto index = map.find(comp); — Blastfurnace
– Blastfurnace, Commented May 13, 2014 at 3:41
@Blastfurnace instead of the const_interator? or in addition to it? — jshah
– jshah, Commented May 13, 2014 at 3:47
I would just use the auto keyword. The compiler already knows the type of the expression map.find(comp) so it will declare index as that type. No more typos on those tedious iterator declarations. — Blastfurnace
– Blastfurnace, Commented May 13, 2014 at 3:52

billz · Accepted Answer · 2014-05-13 03:39:37Z

2

You missed :: in below statement

unordered_map<long,long>const_iterator

should be:

unordered_map<long,long>::const_iterator

answered May 13, 2014 at 3:39

billz

45.6k9 gold badges87 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

jshah Over a year ago

Wow... thanks! I still have another error: in instantiation of function template specialization 'std::__1::unordered_map<long, long, std::__1::hash<long>, std::__1::equal_to<long>, std::__1::allocator<std::__1::pair<const long, long> > >::insert<int>' requested here map.insert(A[i],i);. Do you know what that is?

billz Over a year ago

that's because map.insert(A[i],i);, insert can take pair, not key/value directly

Collectives™ on Stack Overflow

Unordered_map iterator throwing error

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related