题目：

题解：

func countAndSay(n int) string {prev := "1"for i := 2; i <= n; i++ {cur := &strings.Builder{}for j, start := 0, 0; j < len(prev); start = j {for j < len(prev) && prev[j] == prev[start] {j++}cur.WriteString(strconv.Itoa(j - start))cur.WriteByte(prev[start])}prev = cur.String()}return prev
}