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Leetcode - 13. Roman to Integer

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Leetcode 13. Roman to Integer 解題

解題資訊

題目連結

難度 : easy

程式語言 : python, javascript

解題構思

這題的解題思維有兩個部分

  1. 一看到有對應部分 -> hash table

  2. 羅馬字符遇到成對 “ab” 時有兩種狀況

    • a >= b， 則 ans = a + b，Ex: “III” = 3、”XI” = 11
    • b > a， 則 ans = a + b - 2 * a，Ex: “IX” = 1 + 10 - 2* 1 = 9

Code

Python

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class Solution:
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    def romanToInt(self, s: str) -> int:
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        roman_map = {
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            "I":1,
5
            "V":5,
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            "X":10,
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            "L":50,
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            "C":100,
9
            "D":500,
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            "M":1000
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        }
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        last_num =0
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        total = 0
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        for roman in s:
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            current_num = roman_map[roman]
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            total+=current_num
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            if last_num and current_num >  last_num:
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                total -= 2* last_num
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            last_num = current_num
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        return total

python_result

Javascript

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var romanToInt = function(s) {
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  const roman_map = {
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    I: 1,
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    V: 5,
5
    X: 10,
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    L: 50,
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    C: 100,
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    D: 500,
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    M: 1000
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  };
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  const s_len = s.length;
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  let last_num = 0;
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  let total = 0;
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  for (let i = 0; i < s_len; i++) {
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    const current_num = roman_map[s[i]];
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    total += current_num;
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    if (last_num && current_num > last_num) {
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      total -= 2 * last_num;
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    }
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    last_num = current_num;
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  }
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  return total;
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};

javascript_result