481. Magical String

481. Magical String

题目链接：https://leetcode.com/problems...

找规律的题，比较无聊。根据前面的结果来得到下一个数字是多少。两个point：i和j 分别指向字符串和ocuurrence字符串。

public class Solution {
    public int magicalString(int n) {
        if(n == 0)  return 0;
        if(n <= 3)  return 1;
        
        int[] nums = new int[n];
        nums[0] = 1; nums[1] = nums[2] = 2;
        
        int i = 2, j = 3;
        int count = 1;
        while(j < n) {
            // current number: 1->2, 2->1
            int cur = 3 ^ nums[j-1];
            for(int k = 0; k < nums[i] && j < n; k++) {
                nums[j] = cur;
                // count 1
                if(nums[j] == 1) count++;
                j++;
            }
            i++;
        }
        
        return count;
    }
}