Dual Palindromes Mario Cruz (Colombia) & Hugo Rickeboer (Argentina) A number that reads the same from right to left as when read fromleft to right is called a palindrome. The number 12321 is a pal

The Clocks IOI'94 - Day 2 Consider nine clocks arranged in a 3x3 array thusly: |-------| |-------| |-------| | | | | | | | |---O | |---O | | O |

Prime Cryptarithm The following cryptarithm is a multiplication problem that can besolved by substituting digits from a specified set of N digits into thepositions marked with *. If the set of pr

Arithmetic Progressions An arithmetic progression is a sequence of the form a, a+b,a+2b, ..., a+nb where n=0,1,2,3,... . For this problem, a is anon-negative integer and b is a positive integer.

Packing Rectangles IOI 95 The six basic layouts of four rectangles Four rectangles are given. Find the smallest enclosing (new)rectangle into which these four may be fitted without overlapping.

Hamming Codes Rob Kolstad Given N, B, and D: Find a set of N codewords (1 <= N <= 64),each of length B bits (1 <= B <= 8), such that each of the codewordsis at least Hamming distance of D (1 <= D

Preface Numbering A certain book's prefaces are numbered in upper case Roman numerals. Traditional Roman numeral values use a single letter to represent a certain subset of decimal numbers. Here

Runaround Numbers Runaround numbers are integers with unique digits, none of which is zero (e.g., 81362) that also have an interesting property, exemplified by this demonstration: If you start