LeetCode 13 Roman to Integer

lizhaowei213

于 2016-04-06 19:52:06 发布

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本文介绍了一种将罗马数字转换为十进制整数的算法实现，通过一次遍历字符串来完成转换，适用于1到3999范围内的罗马数字。

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13. Roman to Integer

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Total Accepted: 79915 Total Submissions: 205049 Difficulty: Easy

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

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根据罗马数字还原10进制整数。

模拟题

O(n)从左到右扫一遍就行了。

class Solution {
public:
    int romanToInt(string s) 
    {
        int num=0;
        for(int i=0;i<s.size();i++)
        {
                if(s[i]=='I') 
                        num+=1;
                if(s[i]=='V')
                {
                        if(i!=0 && s[i-1]=='I') 
                                num+=3;
                        else 
                                num+=5;
                }
                if(s[i]=='X')
                {
                        if(i!=0 && s[i-1]=='I') 
                                num+=8;
                        else 
                                num+=10;
                }
                if(s[i]=='L')
                {
                        if(i!=0 && s[i-1]=='X') 
                                num+=30;
                        else 
                                num+=50;
                }
                if(s[i]=='C')
                {
                        if(i!=0 && s[i-1]=='X') 
                                num+=80;
                        else 
                                num+=100;
                }
                if(s[i]=='D')
                {
                        if(i!=0 && s[i-1]=='C') 
                                num+=300;
                        else 
                                num+=500;
                }
                if(s[i]=='M') 
                {
                        if(i!=0 && s[i-1]=='C') 
                                num+=800;
                        else 
                                num+=1000;
                }
        }
        return num;
    }
};