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Algorithms - Foundations · 4:55

C++ for Competitive Programming

C++ the way contest programmers use it: fast input and output, integer types and the overflow that bites everyone once. We run CSES Weird Algorithm from 113383 in an int and watch it wrap past INT_MAX into a loop of negative numbers, catch 10^5 * 10^5 going wrong, see the optimiser delete an overflow check, and find where a double's 53 bits stop being enough, all measured on a Mac.

You will learn

Set up fast input and output and avoid flushing in loops
Choose int, long long or __int128 from the range of the values and their products
Explain why signed overflow is undefined behaviour and how unsigned wraparound causes bugs
Avoid floating-point traps in integer problems and debug with sanitizers

Chapters

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