Daily LeetCode – day0094 0481. Magical String

// 0481. Magical String
class Solution {
    public int magicalString(int n) {
        if (n <= 3) return 1;
        int ans = 1;
        int[] magical = new int[n + 1];
        magical[0] = 1;
        magical[1] = magical[2] = 2;
        int slow = 2;
        int fast = 3;
        int fill = 1;
        while (fast < n) {
            for (int i = 0; i < magical[slow]; ++i) {
                magical[fast] = fill;
                if (fill == 1 && fast < n) ++ans;
                ++fast;
            }
            fill = 3 - fill;
            ++slow;
        }
        return ans;
    }
}

学习笔记：
这道题是双指针算法的题目。
快指针写，慢指针读。