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unordered_map::begin

Designates the beginning of the controlled sequence or a bucket.

iterator begin();
const_iterator begin() const;
local_iterator begin(size_type nbucket);
const_local_iterator begin(size_type nbucket) const;

Parameter

Description

nbucket

The bucket number.

The first two member functions return a forward iterator that points at the first element of the sequence (or just beyond the end of an empty sequence). The last two member functions return a forward iterator that points at the first element of bucket nbucket (or just beyond the end of an empty bucket).

// std_tr1__unordered_map__unordered_map_begin.cpp 
// compile with: /EHsc 
#include <unordered_map> 
#include <iostream> 
 
typedef std::unordered_map<char, int> Mymap; 
int main() 
    { 
    Mymap c1; 
 
    c1.insert(Mymap::value_type('a', 1)); 
    c1.insert(Mymap::value_type('b', 2)); 
    c1.insert(Mymap::value_type('c', 3)); 
 
// display contents " [c 3] [b 2] [a 1]" 
    for (Mymap::const_iterator it = c1.begin(); 
        it != c1.end(); ++it) 
        std::cout << " [" << it->first << ", " << it->second << "]"; 
    std::cout << std::endl; 
 
// inspect first two items " [c 3] [b 2]" 
    Mymap::iterator it2 = c1.begin(); 
    std::cout << " [" << it2->first << ", " << it2->second << "]"; 
    ++it2; 
    std::cout << " [" << it2->first << ", " << it2->second << "]"; 
    std::cout << std::endl; 
 
// inspect bucket containing 'a' 
    Mymap::const_local_iterator lit = c1.begin(c1.bucket('a')); 
    std::cout << " [" << lit->first << ", " << lit->second << "]"; 
 
    return (0); 
    } 
 
 [c, 3] [b, 2] [a, 1]
 [c, 3] [b, 2]
 [a, 1]

Header: <unordered_map>

Namespace: std

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