Look and Say Numbers

Published by Mubashir Hassan in
algorithmsmathnumbers

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

  • Split the number into groups of two digit numbers. If the number has an odd number of digits, return "invalid".
  • 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 a string.
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 a string.

Examples

lookAndSay(95) ➞ "555555555"

lookAndSay(120520) ➞ "200"

lookAndSay(231) ➞ "invalid"

Notes

  • Note that the number 0 can be included (see example #3).
  • Check the Resources tab for a TED-Ed video for extra clarity.
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