CODEWITHSUNDEEP
c++dictionarystliterator
adrian008
adrian008

Reputation: 405

Illegal Indirection in C++

I can't figure out why I get an illegal indirection error :

#include <iostream>
#include <algorithm>
#include <stack>
#include <unordered_map>

using namespace std;

int main()
{
    string s1 = "";
    stack<char> s;
    unordered_map<char, char> m;

    m.insert('(', ')');
    m.insert('{', '}');
    m.insert('[', ']');

    for (auto x : s1)
    {
        if (m.find(x) != m.end()) s.push(x);

        else 
        {
            auto it = m.find(s.top());
            if (s.empty() || (it->second) != x) { cout << "Invalid\n"; s.pop(); break; } 
        }

    }

}

it is an iterator to a map entry and I am trying to access its value.

Upvotes: 1

Views: 5501

Answers (2)

Steephen
Steephen

Reputation: 15824

You have to correct your insertion into unordered_map<> as follows:

m.insert(std::make_pair('(', ')'));
m.insert(std::make_pair('{', '}'));
m.insert(std::make_pair('[', ']'));

Demo: http://coliru.stacked-crooked.com/a/a2fff8b2f36ebc3c

A few more options for insertion into unordered_map<>:

m.emplace('(', ')');
m.emplace('{', '}');
m.emplace('[', ']');

OR

m.insert(std::pair<char,char>('(', ')'));
m.insert(std::pair<char,char>('{', '}'));
m.insert(std::pair<char,char>('[', ']'));

EDIT

One more option:

m.emplace(std::make_pair('(', ')'));
m.emplace(std::make_pair('{', '}'));
m.emplace(std::make_pair('[', ']'));

Upvotes: 8

Hatted Rooster
Hatted Rooster

Reputation: 36483

There is another way to "insert" into a map that the original answer hasn't noted which is with the [] operator:

m['('] = ')';
m['{'] = '}';
m['['] = ']';

Upvotes: 4

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