map 与 unordered_map 的遍历

1.while

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map<int, int>::iterator iter;
    iter = _map.begin();
    while(iter != _map.end())
    {
        cout << iter->first << ' ' << iter->second << endl;
        iter++;
    }

2.for(本质上和第一种一样)

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map<int, int>::iterator iter;
for(iter = _map.begin(); iter != _map.end(); iter++)
{
    cout << iter->first << ' ' << iter->second << endl;
}

3. auto

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for(auto v:_map)
    cout << v.first << ' ' << v.second << endl;