IOI 2001
All 4 IOI tasks from 2001, organized as individual solution pages.
Problem set
Each entry below goes straight to the public problem page, with the statement, editorial, code, and raw resources kept together.
Double Crypt
Problem Statement Summary A message is encrypted twice using two different simple ciphers, each parameterized by a key from a known key space: ciphertext = E_ k_2 (E_ k_1 (plaintext)). The key spaces for k_1 and k_2 e...
Ioiwari
Problem Statement Summary Ioiwari is a two-player game played on a triangular board with 10 cells arranged in a triangle of side 4: 0 1 2 3 4 5 6 7 8 9 Each cell initially contains a stone with a distinct value in \ 1...
Mobile Phones
Problem Statement Summary Maintain an S S grid (initially all zeros, S 1024) under two operations: Update(x, y, v): add v to cell (x, y). Query(x_1, y_1, x_2, y_2): return the sum of all cells in the rectangle [x_1, x...
Score
Problem Statement Summary Given a decimal number as a string of N digits and a budget of K adjacent swaps, find the maximum and minimum numbers obtainable. Leading zeros are not permitted (except for the number 0 itse...