用Rust刷leetcode第十三题

Problem

Roman numerals are represented by seven different symbols: ​​I​​​, ​​V​​​, ​​X​​​, ​​L​​​, ​​C​​​, ​​D​​​ and ​​M​​.

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1000

For example, two is written as ​​II​​​ in Roman numeral, just two one’s added together. Twelve is written as, ​​XII​​​, which is simply ​​X​​​ + ​​II​​​. The number twenty seven is written as ​​XXVII​​​, which is ​​XX​​​ + ​​V​​​ + ​​II​​.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not ​​IIII​​​. Instead, the number four is written as ​​IV​​​. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as ​​IX​​. There are six instances where subtraction is used:

• ​​I​​​ can be placed before ​​V​​​ (5) and ​​X​​ (10) to make 4 and 9.
• ​​X​​​ can be placed before ​​L​​​ (50) and ​​C​​ (100) to make 40 and 90.
• ​​C​​​ can be placed before ​​D​​​ (500) and ​​M​​ (1000) to make 400 and 900.

Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.

Example

Example 1:

Input: “III”
Output: 3

Example 2:

Input: “IV”
Output: 4

Example 3:

Input: “IX”
Output: 9

Example 4:

Input: “LVIII”
Output: 58
Explanation: L = 50, V= 5, III = 3.

Example 5:

Input: “MCMXCIV”
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Solution

impl Solution {
    pub fn get_value(c: char) -> i32 {
        match c {
            'I' => return 1,
            'V' => return 5,
            'X' => return 10,
            'L' => return 50,
            'C' => return 100,
            'D' => return 500,
            'M' => return 1000,
            _ => return 0,
        }    
    }
    
    pub fn roman_to_int(s: String) -> i32 {
        let mut ret = 0;
        let mut s1 = s.clone();
        
        let mut temp = "".to_string();
        let mut flag = false;
        
        while s1.len() > 0 {
            let c = s1.remove(0);
            
            if temp.len() == 1 {
                temp.push(c);
                
                flag = false;
                if temp == "CM" {
                    ret += 900;
                } else if temp == "CD" {
                    ret += 400;
                } else if temp == "XC" {
                    ret += 90;
                } else if temp == "XL" {
                    ret += 40;
                } else if temp == "IX" {
                    ret += 9;
                } else if temp == "IV" {
                    ret += 4;
                } else {
                    let cc = temp.remove(0); 
                    ret += Solution::get_value(cc);
                    
                    flag = true;
                }
                
                if flag == false {
                    temp.remove(0);
                    temp.remove(0);
                }

                 
            } else if c == 'C' || c == 'X' || c == 'I' {
                temp.push(c);
            } else {
                ret += Solution::get_value(c);
            }     
        }
        
        while temp.len() > 0 {
            let cc = temp.remove(0); 
            ret += Solution::get_value(cc);
        }
        ret
    }
}