Look And Say Numbers

Published by Deep Xavier in
algorithmsmathnumbers

Given an integer value, return a new integer according to the rules below:

  • Split the number into groups of two digit numbers. If the number has an odd number of digits, return -1.
  • For each group of two digit numbers, concatenate the last digit to a new string the same number of times as the value of the first digit.
  • Return the result as an integer.
lookAndSay(3132) ➞ 111222

// By reading the number digit by digit, you get three "1" and three "2".
// Therefore, you put three ones and three two's together.
// Remember to return an integer value (i.e BigIntger class).

Examples

lookAndSay(1213200012171979) ➞ 23002799999999

lookAndSay(54544666) ➞ 44444444446666666666

lookAndSay(95) ➞ 555555555

lookAndSay(1213141516171819) ➞ 23456789

lookAndSay(120520) ➞ 200

lookAndSay(231) ➞ -1

Notes

  • Note that the number 0 can be included (see example #5).
  • Check the Resources tab for a TED-Ed video for extra clarity.
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