LeetCode——Roman To Integer

原创于 2013-06-07 17:26:37 发布 · 685 阅读

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本文介绍了一种将罗马数字转换为整数的有效算法。通过建立一个常数表，该算法能够快速处理输入的罗马数字，并确保转换结果的准确性。输入范围限定在1到3999之间。

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Given a roman numeral, convert it to an integer.

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

» Solve this problem

同Integer To Roman一题一样，建立常数表，直接处理。

class Solution {
public:
    const string romans[4][10] = {
        {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"},
        {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"},
        {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"},
        {"", "M", "MM", "MMM", "", "", "", "", "", ""}
    };
    
    int romanToInt(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int ans = 0, power = 1000;
        int head = 0, idx = 3;
        string temp;
        while (head < s.size()) {
            for (int i = 9; i >= 1; i--) {
                int length = romans[idx][i].size();
                if (length != 0 && head + length <= s.size()) {
                    temp = s.substr(head, length);
	            if (temp == romans[idx][i]) {
	                ans += i * power;                    
    	                head += length;
	                break;
    	            }
    	        }
            }
            idx--;
            power /= 10;
        }
        return ans;
    }
};