-
Notifications
You must be signed in to change notification settings - Fork 0
/
13.cpp
81 lines (73 loc) · 2.46 KB
/
13.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
// 13. Roman to Integer
// Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
// Symbol Value
// I 1
// V 5
// X 10
// L 50
// C 100
// D 500
// M 1000
// For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.
// Roman numerals are usually written largest to smallest from left to right.
// However, the numeral for four is not IIII.
// Instead, the number four is written as IV.
// Because the one is before the five we subtract it making four.
// The same principle applies to the number nine,
// which is written as IX. There are six instances where subtraction is used:
// I can be placed before V (5) and X (10) to make 4 and 9.
// X can be placed before L (50) and C (100) to make 40 and 90.
// C can be placed before D (500) and M (1000) to make 400 and 900.
// Given a roman numeral, convert it to an integer.
// Input is guaranteed to be within the range from 1 to 3999.
#include <iostream>
#include <unordered_map>
using namespace std;
class Solution
{
public:
int romanToInt(string s)
{
int result = 0;
unordered_map<char, int> hash;
hash['I'] = 1;
hash['V'] = 5;
hash['X'] = 10;
hash['L'] = 50;
hash['C'] = 100;
hash['D'] = 500;
hash['M'] = 1000;
// iter from right to left III
for (int i = (s.size() - 1); i > -1; i--)
{
// Roman numerals are usually written largest to smallest
// from left to right. If not means special case(IV=4 or IX=9)
if (i > 0 && hash[s[i]] > hash[s[i - 1]])
{
// minors two times of s[i-1] because next will add s[i-1]
result += hash[s[i]] - hash[s[i - 1]] * 2;
}
else
{
result += hash[s[i]];
}
}
return result;
}
};
int main()
{
Solution s = Solution();
int ans = 0;
ans = s.romanToInt("III");
std::cout << ans << std::endl;
ans = s.romanToInt("IV");
std::cout << ans << std::endl;
ans = s.romanToInt("IX");
std::cout << ans << std::endl;
ans = s.romanToInt("LVIII");
std::cout << ans << std::endl;
ans = s.romanToInt("MCMXCIV");
std::cout << ans << std::endl;
return 0;
}