Support display sup/sub style for numbers

[hulufei]

For example: leetcode problem 202

[clearloop]

Thanks!!!

 𝝺 pcs cargo run p 202
    Finished dev [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/leetcode p 202`

[202] Happy Number is on the run...


Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

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Example: 


Input: 19
Output: true
Explanation: 
1² + 9² = 82
8² + 2² = 68
6² + 8² = 100
1² + 0² + 0² = 1

[clearloop]

We can write like:

pub fn superscript(n: u8) -> String {
        match n {
            0 => "⁰".to_string(),
            1 => "¹".to_string(),
            2 => "²".to_string(),
            3 => "³".to_string(),
            4 => "⁴".to_string(),
            5 => "⁵".to_string(),
            6 => "⁶".to_string(),
            7 => "⁷".to_string(),
            8 => "⁸".to_string(),
            9 => "⁹".to_string(),
            x if x > 10 => (superscript(n / 10).parse().unwrap_or(0)
                + &superscript(n % 10).parse().unwrap_or(0))
                .to_string(),
            _ => n.to_string(),
        }
    }
}