Dual PalindromesMario 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 ClocksIOI'94 - Day 2Consider nine clocks arranged in a 3x3 array thusly:|-------| |-------| |-------| | | | | | | | |---O | |---O | | O |

Prime CryptarithmThe 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 ProgressionsAn 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 RectanglesIOI 95The six basic layouts of four rectanglesFour rectangles are given. Find the smallest enclosing (new)rectangle into which these four may be fitted without overlapping.

Hamming CodesRob KolstadGiven 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 NumberingA 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 NumbersRunaround 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