Package g0401_0500.s0481_magical_string

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    481 - Magical String.

    Medium

    A magical string s consists of only '1' and '2' and obeys the following rules:

    • The string s is magical because concatenating the number of contiguous occurrences of characters '1' and '2' generates the string s itself.

    The first few elements of s is s = "1221121221221121122……". If we group the consecutive 1's and 2's in s, it will be "1 22 11 2 1 22 1 22 11 2 11 22 ......" and the occurrences of 1's or 2's in each group are "1 2 2 1 1 2 1 2 2 1 2 2 ......". You can see that the occurrence sequence is s itself.

    Given an integer n, return the number of 1's in the first n number in the magical string s.

    Example 1:

    Input: n = 6

    Output: 3

    Explanation: The first 6 elements of magical string s is "122112" and it contains three 1's, so return 3.

    Example 2:

    Input: n = 1

    Output: 1

    Constraints:

    • <code>1 <= n <= 10<sup>5</sup></code>

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer magicalString(Integer n)

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait