C++ Loop through Map

Question

I want to iterate through each element in the map<string, int> without knowing any of its string-int values or keys.

What I have so far:

void output(map<string, int> table) {        map<string, int>::iterator it;        for (it = table.begin(); it != table.end(); it++)        {             //How do I access each element?          } } 

Answer 1

You can achieve this like following :

map<string, int>::iterator it;  for (it = symbolTable.begin(); it != symbolTable.end(); it++) {     std::cout << it->first    // string (key)               << ':'               << it->second   // string's value                << std::endl; } 

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With C++11 _{( and onwards )},

for (auto const& x : symbolTable) {     std::cout << x.first  // string (key)               << ':'                << x.second // string's value                << std::endl; } 

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With C++17 _{( and onwards )},

for (auto const& [key, val] : symbolTable) {     std::cout << key        // string (key)               << ':'                 << val        // string's value               << std::endl; } 

Answer 2

Try the following

for ( const auto &p : table ) {    std::cout << p.first << '\t' << p.second << std::endl; }  

The same can be written using an ordinary for loop

for ( auto it = table.begin(); it != table.end(); ++it  ) {    std::cout << it->first << '\t' << it->second << std::endl; }  

Take into account that value_type for std::map is defined the following way

typedef pair<const Key, T> value_type 

Thus in my example p is a const reference to the value_type where Key is std::string and T is int

Also it would be better if the function would be declared as

void output( const map<string, int> &table );