CurriculumUnordered Containers
Unordered Containers
Containers like <code>std::unordered_map</code> and <code>std::unordered_set</code> do not sort their elements. Instead, they use Hash Tables to achieve O(1) constant-time lookups!
011. Basics
Unordered containers use hash tables for fast average lookup and do not maintain sorted iteration order.
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022. Adding Elements
Add values with the container's insertion operation and observe the ordering or adapter rule.
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033. Access and Lookup
Read values safely with the appropriate access API before removing or changing them.
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044. Iteration
Understand the traversal guarantee: sorted for ordered containers, FIFO/LIFO for adapters, and unspecified for hash tables.
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055. Removal
Remove by value, iterator, or end operation as appropriate; always check preconditions for empty adapters.
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066. Size and Empty
Use
size and empty to make control flow safe and explicit.main.cpp
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077. Applied Logic
This example exercises a small calculation or data-processing pattern with the container.
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088. Complexity
Choose the container based on the operation you perform most often, not just on familiar syntax.
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099. Practical Pattern
Use the container to model a real structure such as inventory, a task stream, an undo history, or a sliding window.
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1010. Pro Tip
Reserve capacity before a known large insertion batch to reduce rehashes.
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AI Tutor
If you don't care about the order of elements (e.g., printing them alphabetically), unordered containers are significantly faster than standard maps/sets for massive datasets.