Leetcode 1980 - Cantor's Diagonal Argument

lib.rs

use std::collections::HashSet;

pub struct Solution;

impl Solution {
    pub fn find_different_binary_string(nums: Vec<String>) -> String {
        let n = nums.len();
        let nums = nums
            .iter()
            .map(|s| usize::from_str_radix(s, 2).unwrap())
            .collect::<HashSet<usize>>();

        for i in 0..=n {
            if !nums.contains(&i) {
                return format!("{:0>n$b}", i, n = n);
            }
        }

        unreachable!();
    }

    pub fn cantors_diagonal(nums: Vec<String>) -> String {
        nums.iter()
            .enumerate()
            .map(|(i, n)| n.as_bytes()[i])
            .map(|b| if b == b'0' { '1' } else { '0' })
            .collect()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_find_different_binary_string() {
        assert_eq!(
            Solution::find_different_binary_string(vec!["01".to_string(), "10".to_string()]),
            "00"
        );
        assert_eq!(
            Solution::find_different_binary_string(vec!["00".to_string(), "01".to_string()]),
            "10"
        );
        assert_eq!(
            Solution::find_different_binary_string(vec![
                "111".to_string(),
                "011".to_string(),
                "001".to_string()
            ]),
            "000"
        );
    }

    #[test]
    fn test_cantors_diagonal() {
        assert_eq!(
            Solution::cantors_diagonal(vec!["01".to_string(), "10".to_string()]),
            "11"
        );
        assert_eq!(
            Solution::cantors_diagonal(vec!["00".to_string(), "01".to_string()]),
            "10"
        );
        assert_eq!(
            Solution::cantors_diagonal(vec![
                "111".to_string(),
                "011".to_string(),
                "001".to_string()
            ]),
            "000"
        );
    }
}