Leetcode: Roman to Integer

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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.

利用上一题的程序：

Judge Small： Accepted!

Judge Large：Time Limit Exceeded

map<string,int> romanmp;    void romanstr(string& roman, int num, char* symbol){if(num == 0)return;else if(num <= 3) roman.append(num, *symbol);else if(num == 4){roman.append(1,*symbol);roman.append(1,*(symbol+1));}else if(num <= 8){roman.append(1,*(symbol+1));roman.append(num-5,*symbol);}else if(num == 9){roman.append(1,*symbol);roman.append(1,*(symbol+2));}}string intToRoman(int num) {        // Start typing your C/C++ solution below        // DO NOT write int main() function            char symbol[9] = {'I','V','X','L','C','D','M'};        string roman="";int scale = 1000;int p=6;while(num){int bit = num/scale;romanstr(roman, bit, symbol+p);num = num%scale;scale /= 10;p -= 2;}return roman;    }int romanToInt(string s) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        for(int i = 0;i <4000; i++)romanmp[intToRoman(i)] = i;return romanmp[s];    }

Accepted!

int romanToInt(string s) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int length = s.length();    if(length <1) return 0;map<char,int> m;m['I'] = 1;m['V'] = 5;m['X'] = 10;m['L'] = 50;m['C'] = 100;m['D'] = 500;m['M'] = 1000;int i = length-1;int sum = m[s[i--]];while(i>=0)if(m[s[i+1]] > m[s[i]])sum -= m[s[i--]];elsesum += m[s[i--]];return sum;    }