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57-catching-car-mileage-numbers.md

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Problem:

"7777...8?!??!", exclaimed Bob, "I missed it again! Argh!" Every time there's an interesting number coming up, he notices and then promptly forgets. Who doesn't like catching those one-off interesting mileage numbers?

Let's make it so Bob never misses another interesting number. We've hacked into his car's computer, and we have a box hooked up that reads mileage numbers. We've got a box glued to his dash that lights up yellow or green depending on whether it receives a 1 or a 2 (respectively).

It's up to you, intrepid warrior, to glue the parts together. Write the function that parses the mileage number input, and returns a 2 if the number is "interesting" (see below), a 1 if an interesting number occurs within the next two miles, or a 0 if the number is not interesting.

Note: In Haskell, we use No, Almost and Yes instead of 0, 1 and 2.

"Interesting" Numbers

Interesting numbers are 3-or-more digit numbers that meet one or more of the following criteria:

  • Any digit followed by all zeros: 100, 90000
  • Every digit is the same number: 1111
  • The digits are sequential, incementing†: 1234
  • The digits are sequential, decrementing‡: 4321
  • The digits are a palindrome: 1221 or 73837
  • The digits match one of the values in the awesomePhrases array

† For incrementing sequences, 0 should come after 9, and not before 1, as in 7890.
‡ For decrementing sequences, 0 should come after 1, and not before 9, as in 3210.

So, you should expect these inputs and outputs:

// "boring" numbers
isInteresting(3, [1337, 256]);    // 0
isInteresting(3236, [1337, 256]); // 0

// progress as we near an "interesting" number
isInteresting(11207, []); // 0
isInteresting(11208, []); // 0
isInteresting(11209, []); // 1
isInteresting(11210, []); // 1
isInteresting(11211, []); // 2


// nearing a provided "awesome phrase"
isInteresting(1335, [1337, 256]); // 1
isInteresting(1336, [1337, 256]); // 1
isInteresting(1337, [1337, 256]); // 2

-- "boring" numbers
isInteresting 3     [1337, 256] -- 0
isInteresting 3236  [1337, 256] -- 0

-- progress as we near an "interesting" number
isInteresting 11207  [] -- No 
isInteresting 11208  [] -- No 
isInteresting 11209  [] -- Almost
isInteresting 11210  [] -- Almost
isInteresting 11211  [] -- Yes

-- nearing a provided "awesome phrase"
isInteresting 1335  [1337, 256] -- Almost
isInteresting 1336  [1337, 256] -- Almost
isInteresting 1337  [1337, 256] -- Yes
# "boring" numbers
isInteresting(3, [1337, 256])    # 0
isInteresting(3236, [1337, 256]) # 0

# progress as we near an "interesting" number
isInteresting(11207, []) # 0
isInteresting(11208, []) # 0
isInteresting(11209, []) # 1
isInteresting(11210, []) # 1
isInteresting(11211, []) # 2

# nearing a provided "awesome phrase"
isInteresting(1335, [1337, 256]) # 1
isInteresting(1336, [1337, 256]) # 1
isInteresting(1337, [1337, 256]) # 2
// "boring" numbers
CarMileage.isInteresting(3, new int[]{1337, 256});    // 0
CarMileage.isInteresting(3236, new int[]{1337, 256}); // 0

// progress as we near an "interesting" number
CarMileage.isInteresting(11207, new int[]{}); // 0
CarMileage.isInteresting(11208, new int[]{}); // 0
CarMileage.isInteresting(11209, new int[]{}); // 1
CarMileage.isInteresting(11210, new int[]{}); // 1
CarMileage.isInteresting(11211, new int[]{}); // 2

// nearing a provided "awesome phrase"
CarMileage.isInteresting(1335, new int[]{1337, 256}); // 1
CarMileage.isInteresting(1336, new int[]{1337, 256}); // 1
CarMileage.isInteresting(1337, new int[]{1337, 256}); // 2
# "boring" numbers
is_interesting(3, [1337, 256])    # 0
is_interesting(3236, [1337, 256]) # 0

# progress as we near an "interesting" number
is_interesting(11207, []) # 0
is_interesting(11208, []) # 0
is_interesting(11209, []) # 1
is_interesting(11210, []) # 1
is_interesting(11211, []) # 2

# nearing a provided "awesome phrase"
is_interesting(1335, [1337, 256]) # 1
is_interesting(1336, [1337, 256]) # 1
is_interesting(1337, [1337, 256]) # 2
# "boring" numbers
is_interesting(3, [1337, 256])    # 0
is_interesting(3236, [1337, 256]) # 0

# progress as we near an "interesting" number
is_interesting(11207, []) # 0
is_interesting(11208, []) # 0
is_interesting(11209, []) # 1
is_interesting(11210, []) # 1
is_interesting(11211, []) # 2

# nearing a provided "awesome phrase"
is_interesting(1335, [1337, 256]) # 1
is_interesting(1336, [1337, 256]) # 1
is_interesting(1337, [1337, 256]) # 2
// "boring" numbers
Kata.IsInteresting(3, new List<int>() { 1337, 256 });    // 0
Kata.IsInteresting(3236, new List<int>() { 1337, 256 }); // 0

// progress as we near an "interesting" number
Kata.IsInteresting(11207, new List<int>() { });   // 0
Kata.IsInteresting(11208, new List<int>() { });   // 0
Kata.IsInteresting(11209, new List<int>() { });   // 1
Kata.IsInteresting(11210, new List<int>() { });   // 1
Kata.IsInteresting(11211, new List<int>() { });   // 2

// nearing a provided "awesome phrase"
Kata.IsInteresting(1335, new List<int>() { 1337, 256 });   // 1
Kata.IsInteresting(1336, new List<int>() { 1337, 256 });   // 1
Kata.IsInteresting(1337, new List<int>() { 1337, 256 });   // 2

Error Checking

  • A number is only interesting if it is greater than 99!
  • Input will always be an integer greater than 0, and less than 1,000,000,000.
  • The awesomePhrases array will always be provided, and will always be an array, but may be empty. (Not everyone thinks numbers spell funny words...)
  • You should only ever output 0, 1, or 2.

Solution