Advent of PBT 2021 - Day 17 - Solution

Our algorithm was: isHumbleNumber.
Go to the subject itself for more details

CodeSandbox with a possible set of properties you may have come with: https://codesandbox.io/s/advent-of-pbt-day-17-solution-75tuu?file=/src/index.spec.ts&previewwindow=tests

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Property 1: should consider any composite of primes <=7 as humble

for any number n product of factors <=7
it should consider n as an humble number

Written with fast-check:

it("should consider any composite of primes <=7 as humble", () => {
  fc.assert(
    fc.property(
      fc.array(fc.integer({ min: 2, max: 7 }), { minLength: 1 }),
      (factors) => {
        // Arrange
        let n = 1;
        for (const f of factors) {
          if (n * f > 2 ** 31 - 1) break;
          n = n * f;
        }

        // Act / Assert
        expect(isHumbleNumber(n)).toBe(true);
      }
    )
  );
});

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Property 2: should consider any composite with one prime factor >7 as non-humble

for any number n with at least one factor not divisible by any number in [2, 7]
it should consider n as a non-humble number

Written with fast-check:

it("should consider any composite with one prime factor >7 as non-humble", () => {
  fc.assert(
    fc.property(
      fc
        .integer({ min: 11 }) // 8,9,10 would be filtered
        .filter((v) => v % 2 !== 0)
        .filter((v) => v % 3 !== 0)
        .filter((v) => v % 5 !== 0)
        .filter((v) => v % 7 !== 0),
      fc.array(fc.integer({ min: 1, max: 195225786 })),
      (tooLarge, factors) => {
        // Arrange
        let n = tooLarge;
        for (const f of factors) {
          if (n * f > 2 ** 31 - 1) break;
          n = n * f;
        }

        // Act / Assert
        expect(isHumbleNumber(n)).toBe(false);
      }
    )
  );
});

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Back to "Advent of PBT 2021" to see topics covered during the other days and their solutions.

More about this serie on @ndubien or with the hashtag #AdventOfPBT.