CODEWITHSUNDEEP
c++dictionaryiterator
Josh
Josh

Reputation: 3321

Map iterators traversal technique

I was having problem declaring an iterator to traverse through a map and find values. I'm getting a error of "expected initializer before 'fibiter'".

map <int, int> fibHash;

int memoized_fib(int n)
{
    map <int, int> iterator fibiter = fibHash.find(n); //ERROR HERE

    if(fibiter != fibHash.end())
        return  *fibiter;

    int fib_val;
    if(n  <= 1)
        fib_val = 1;
    else
        fib_val = memoized_fib(n - 1) + memoized_fib(n - 2);

    fibHash[n] = fib_val;
    return fib_val;
}

int main()
[..]

Upvotes: 1

Views: 113

Answers (2)

Puppy
Puppy

Reputation: 147046

You forgot to use the scope resolution operator, ::. The compiler thinks you declared a map<int, int> named iterator, and therefore gets mighty confused when it finds fibiter.

map<int, int>::iterator fibiter

is what you want

Upvotes: 4

qdii
qdii

Reputation: 12983

map <int, int> iterator → map <int, int>::iterator

iterator is a typedef defined within the class "map". You can look that up on the implementation of the standard library shipped with GCC 4.6.3 in <bits/stl_map.h> line 139, you have:

typedef typename _Rep_type::iterator               iterator;

As the typedef belongs to the definition of the class, you should add the ":" so that the compiler knows where to find it.

Upvotes: 1

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