# Exercise 5: smallest divisible number

Exercise 5: smallest divisible number

What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

/* 2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20? */ // It seems the only way to do this is by exhaustive again. So we count up and // look for the first success. However, we don't have to check for all the // divisors - if something is divisible by 20, it is also divisible by 10 and // 5 and 4 and 2 ... divisors = [20, 19, 18, 17, 16, 14, 13, 12, 11] num_divisors = divisors.size() // We get a speedup by "stepping-up" by the smallest divisor. This also means // that we don't have to test for that divisor step = divisors[-1] for (i=step;; i=i+step) { found_all_div = true for (j=0; j < (num_divisors - 1); j++) { d = divisors[j] if (i % d != 0) { // println ("\${i} is not divisible by \${d} ...") found_all_div = false break } } if (found_all_div) { println i // => 232792560 break } }