longest-common-prefix.rs

// https://leetcode.com/problems/longest-common-prefix/

impl Solution {
    pub fn longest_common_prefix(strs: Vec<String>) -> String {
        let mut ret = String::from("");
        let mut idx = 0;
        let mut other_char;
        loop {
            other_char = None;
            for str in &strs {
                if let Some(c) = str.chars().nth(idx) {
                    if other_char.is_none() {
                        other_char = Some(c);
                    } else if c != other_char.unwrap() {
                        return ret;
                    }
                } else {
                    return ret;
                }
            }
            ret.push(other_char.unwrap());
            idx += 1;
        }
    }
}

palindrome-number.rs

// https://leetcode.com/problems/palindrome-number/

impl Solution {
    pub fn is_palindrome(x: i32) -> bool {
        if x < 0 {
            return false;
        }
        let mut x = x;
        let mut digits = vec![];
        while x > 0 {
            digits.push(x % 10);
            x = x / 10;
        }
        let mut rev_digits = digits.clone();
        rev_digits.reverse();
        return digits == rev_digits;
    }
}

roman-to-integer.rs

// https://leetcode.com/problems/roman-to-integer/

impl Solution {
    pub fn roman_to_int(s: String) -> i32 {
        let mut ret = 0;
        let mut last_char = ' ';
        for c in s.chars() {
            match c {
                'M' => if last_char == 'C' {
                        ret += 900 - 100;
                    } else {
                        ret += 1000;
                    },
                'D' => if last_char == 'C' {
                        ret += 400 - 100;
                    } else {
                        ret += 500;
                    },
                'C' => if last_char == 'X' {
                        ret += 90 - 10;
                    } else {
                        ret += 100;
                    },
                'L' => if last_char == 'X' {
                        ret += 40 - 10;
                    } else {
                        ret += 50;
                    },
                'X' => if last_char == 'I' {
                        ret += 9 - 1;
                    } else {
                        ret += 10;
                    },
                'V' => if last_char == 'I' {
                        ret += 4 - 1;
                    } else {
                        ret += 5;
                    },
                'I' => ret += 1,
                _ => panic!("unknown roman numeral")
            }
            last_char = c;
        }
        return ret;
    }
}