Algorithm

Input/Output & Fast I/O Boilerplates

Language Basics & Mechanics Pattern

Input/Output & Fast I/O Boilerplates

Standard templates for reading input and printing output efficiently across competitive programming platforms like LeetCode, Codeforces, and HackerRank.

CONSTRAINTS
  • C++: ios_base::sync_with_stdio(false); cin.tie(NULL);
  • Java: BufferedReader + StringTokenizer vs Scanner
  • Python: sys.stdin.read().split()
EXAMPLE 1
Input: Reading 1,000,000 integers
Output: Fast I/O executes in ~0.05s vs Scanner/cin taking > 1.5s
Buffered I/O reads chunks of bytes into RAM at once instead of making individual system calls per character.
Does LeetCode require fast I/O code?
On LeetCode, function signatures pass inputs pre-parsed as arguments, but adding fast I/O speedups at the top of C++ files can reduce submission runtime.

On competitive programming platforms, slow standard I/O (like Java's Scanner or C++'s std::endl flushing) can cause Time Limit Exceeded (TLE) even if your algorithm is correct.

Fast I/O Rules

- C++: Disable synchronization with C I/O streams using ios_base::sync_with_stdio(false); cin.tie(NULL);. Avoid endl (use \n).
- Java: Replace Scanner with BufferedReader and StringTokenizer.
- Python: Use sys.stdin.readline or sys.stdin.read().split().

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Fast I/O templates.