# 13. Roman to Integer
Difficulty: Easy

## Solution

/**
*** Author: R-CO
*** E-mail: [e-mail]
*** Date: 2020-11-09
**/

#define VERSION_0 0
#define VERSION_1 (VERSION_0 == 0)

#if VERSION_0
#include <cstdlib>
#include <string>
using std::string;
#include <unordered_map>
using std::unordered_map;

using RefMap = unordered_map<char, int>;

class Solution {
 public:
  int romanToInt(string s) {
    int output = 0;

    int previous_value = 0;
    for (auto it = s.rbegin(); it != s.rend(); ++it) {
      int current_value = ref_map[*it];
      if (current_value >= previous_value) {
        output += current_value;
      } else {
        output -= current_value;
      }
      previous_value = current_value;
    }

    return output;
  }

 private:
  RefMap ref_map{{{'I', 1},
                  {'V', 5},
                  {'X', 10},
                  {'L', 50},
                  {'C', 100},
                  {'D', 500},
                  {'M', 1000}}};
};

#elif VERSION_1
#include <string>
using std::string;

class Solution {
 public:
  Solution() {
    ref_map['I'] = 1;
    ref_map['V'] = 5;
    ref_map['X'] = 10;
    ref_map['L'] = 50;
    ref_map['C'] = 100;
    ref_map['D'] = 500;
    ref_map['M'] = 1000;
  }

  int romanToInt(string s) {
    int output = 0;

    int previous_value = 0;
    for (auto it = s.rbegin(); it != s.rend(); ++it) {
      int current_value = ref_map[*it];
      if (current_value >= previous_value) {
        output += current_value;
      } else {
        output -= current_value;
      }
      previous_value = current_value;
    }

    return output;
  }

 private:
  int ref_map['Z'+1];
};

#endif

#include <iostream>
using std::cout;
using std::endl;
#include <vector>
using std::vector;

struct TestCaseStruct {
  string input;
  int expected_output;
};

int main(int argc, char *argv[]) {
  vector<TestCaseStruct> test_cases = {{"III", 3},        {"IV", 4},
                                       {"IX", 9},         {"LVIII", 58},
                                       {"MCMXCIV", 1994}, {"XCIX", 99}};

  Solution solution;
  size_t test_case_index = 0;
  for (auto &test_case : test_cases) {
    if (solution.romanToInt(test_case.input) == test_case.expected_output) {
      cout << "Test case [" << test_case_index << "] is pass." << endl;
    } else {
      cout << "Test case [" << test_case_index << "] is fail." << endl;
    }

    ++test_case_index;
  }

  return EXIT_SUCCESS;
}

## Result
- VERISON_1
Success
Details
Runtime: 24ms, faster than 44.19% of C++ online submissions for Roman to Integer.
Memory Usage: 6.2 MB, less than 5.20% of C++ online submissions for Roman to Integer.

- VERSION_2
Success
Details
Runtime: 4 ms, faster than 94.23% of C++ online submissions for Roman to Integer.
Memory Usage: 6.2 MB, less than 5.20% of C++ online submissions for Roman to Integer.

###### tags: `LeetCode-Easy` `C++`