g0401_0500.s0481_magical_string

Class Solution

java.lang.Object

g0401_0500.s0481_magical_string.Solution

public class Solution
extends Object

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:

• 1 <= n <= 105

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	magicalString(int n)

Methods inherited from class java.lang.Object

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

Constructor Detail

Solution

public Solution()

Method Detail

magicalString

public int magicalString(int n)