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Asked: 2026-05-20T12:18:18+00:00

I’d like to implement the following data structure in c++ (pseudo code): Map<Integer, Integer>

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I’d like to implement the following data structure in c++ (pseudo code):

Map<Integer, Integer>    // Key->Value pairs

Map.put(1,6);
Map.put(2,5);
Map.put(6,89);
Map.put(7,23);
... etc ...

Map.get(2) .... returns 5

In other words, given pairs of integers, where one of them is a look-up key, what is the fastest library implementation that lets me retrieve the Value from one of the Keys? The opposite search of Value->Key is not required.

The size of this map would likely be on the order of 10 000 elements.

I assume a binary tree search will yield the fastest lookup time?
Is std:map the best tool to use? Does boost present any alternatives?

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1 Answer

  1. Editorial Team

    Use an unordered_map (hashmap) or map (binary tree) – Likely unordered_map will be faster. Also, if your key value is limited to 10000, a vector<int> will guarantee constant-time lookup – Use a “magic” value for vector elements that should be “not present”.

    unordered_map is a part of TR1 and c++0x – it is not standard in c++03. Many implementations support it though. Boost also has an unordered_map.

    map and vector are both standard.

    • map corresponds to java TreeMap
    • unordered_map corresponds to java HashMap
    • vector corresponds to java ArrayList
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