# Integer to Roman

#1

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 an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.

Example 1:

```Input: 3
Output: "III"```

Example 2:

```Input: 4
Output: "IV"```

Example 3:

```Input: 9
Output: "IX"```

Example 4:

```Input: 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.
```

Example 5:

```Input: 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.```

#2

The below algorithm uses a pre-defined list of all integers to roman values mapping to generate a roman number for a given number.

Apart from having the basic numbers like `1000, 500, 100 etc`, we should also have the numbers like `900, 400, 90 etc` in our pre-defined list to have a short roman number.

For example, if you don’t have the numbers mentioned above, `9` will be `VIIII` instead of `IX`.

``````func intToRoman(num int) string {
vals := []int{1,4, 5, 9 , 10, 40, 50, 90, 100, 400, 500, 900, 1000}
m := map[int]string{
1 : "I", 4 :"IV", 5 : "V", 9 : "IX", 10: "X",40 :"XL", 50: "L",90: "XC", 100: "C",400 : "CD", 500: "D", 900: "CM", 1000: "M",
}

var result strings.Builder
for i:=len(vals)-1;i>=0;i--{
for vals[i]<=num && num>0{
num = num-vals[i]
result.WriteString(m[vals[i]])
}
}

return result.String()
}
``````

#3

Similar approach in Java.

``````class Solution {
public String intToRoman(int num) {
int[] vals = {1,4, 5, 9 , 10, 40, 50, 90, 100, 400, 500, 900, 1000};
Map<Integer, String> map = new HashMap<>();
map.put(1 , "I");  map.put(4 ,"IV"); map.put(5 , "V");
map.put(9 , "IX");  map.put(10 ,"X");  map.put(40 , "XL");  map.put(50 , "L"); map.put(1000 , "M");
map.put(90 , "XC");  map.put(100 ,"C");  map.put(400 , "CD");  map.put(500 , "D");  map.put(900 , "CM");
StringBuilder result = new StringBuilder();
for(int i=vals.length-1;i>=0;i--){
while(num>0 && vals[i]<=num){
num = num-vals[i];
result.append(map.get(vals[i]));
}
}

return result.toString();
}
}
``````