Unordered_map Find Function

[Shashank_Choudhary]

Hi ,
'
I am trying to compile the following code ,

std::unordered_map<char ,char> mappings = {{')', '('}, {'}' , '{'} , {']','['}};
        std::stack<char> Stack;
        for(int i = 0; i < s.length() ; ++i)
        {
            char c = s.at(i);
            if(mappings.find(c) != s.end()) // ERROR !!!
            {
            ...
            }
        }

I get the following error ,
Invalid operands to binary expression ('std::unordered_map<char, char>::iterator' (aka '__hash_map_iterator<__hash_iterator<std::__hash_node<std::__hash_value_type<char, char>, void *> *>>') and 'std::basic_string<char>::iterator' (aka '__wrap_iter<char *>'))

I think I am comparing the wrong iterators in the "if" loop but I don't see why ? Any help would be much appreciated.
Thank you

 

[WZhang]

Hi ,
'
I am trying to compile the following code ,

std::unordered_map<char ,char> mappings = {{')', '('}, {'}' , '{'} , {']','['}};
        std::stack<char> Stack;
        for(int i = 0; i < s.length() ; ++i)
        {
            char c = s.at(i);
            if(mappings.find(c) != s.end()) // ERROR !!!
            {
            ...
            }
        }

I get the following error ,
Invalid operands to binary expression ('std::unordered_map<char, char>::iterator' (aka '__hash_map_iterator<__hash_iterator<std::__hash_node<std::__hash_value_type<char, char>, void *> *>>') and 'std::basic_string<char>::iterator' (aka '__wrap_iter<char *>'))

I think I am comparing the wrong iterators in the "if" loop but I don't see why ? Any help would be much appreciated.
Thank you

Yes, s.end() (which is the string) will never be the same iterator with the keyset in unordered. Compare it mappings.end() instead of s.end() will resolve this issue.

 

[Shashank_Choudhary]

Yes, s.end() (which is the string) will never be the same iterator with the keyset in unordered. Compare it mappings.end() instead of s.end() will resolve this issue.

Hi , thank you for the reply but the error persists