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Algorithms - Strings · 4:14
C++ Strings
A std::string is an array of chars with a size and a capacity: on this Mac (libc++) the object is 24 bytes and keeps up to 22 characters inline, then spills to a heap buffer whose capacity roughly doubles, so += is amortized O(1) while s = s + c is quadratic (measured). A std::string_view is just a pointer and a length: substr is O(1) with no copy, but the view dangles when the string reallocates, which AddressSanitizer reports as heap-use-after-free. We parse "35=D|55=AAPL|38=100|" into tag/value views with zero calls to operator new, turn digits into numbers with x = x * 10 + (c - '0'), and collect the everyday traps: stoi overflow, size() - 1 on an empty string, signed char and getline after cin >>.
You will learn
- Describe how std::string stores its characters (inline small-string buffer vs heap buffer with doubling capacity) and what push_back, +=, s + c and substr cost
- Use std::string_view for O(1), allocation-free slicing and recognise when a view dangles
- Parse delimited tag=value text in one linear scan, converting digits with x = x * 10 + (c - '0') or std::from_chars
- Avoid the classic traps: stoi overflow, unsigned size() - 1, signed char as an index, and getline after cin >>