Ruby | もんセレクション

問23：非過剰数和

今回の問題 Non-abundant sums A perfect number is a number for which the sum of its proper divisors is exactly equal […]

今回の問題 Names scores Using names.txt (right click and ‘Save Link/Target As…’), a 46K text file […]

今回の問題 Amicable numbers Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divid […]

今回の問題 Factorial digit sum n! means n × (n − 1) × … × 3 × 2 × 1 For example, 10! = 10 × 9 × … × 3 × […]

今回の問題 Counting Sundays You are given the following information, but you may prefer to do some research for you […]

今回の問題 Maximum path sum I By starting at the top of the triangle below and moving to adjacent numbers on the ro […]

今回の問題 Number letter counts If the numbers 1 to 5 are written out in words: one, two, three, four, five, then t […]

今回の問題 Power digit sum 2**15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26. What is the sum of th […]

今回の問題 Lattice paths Starting in the top left corner of a 2×2 grid, and only being able to move to the right an […]

今回の問題 Longest Collatz sequence The following iterative sequence is defined for the set of positive integers: n […]