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IntegerToRoman.java
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package com.yangchd.leetcode.medium;
/**
* @author yangchd 2018/4/27.
*
* 12. Integer to Roman
*
* 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: C = 100, L = 50, XXX = 30 and III = 3.
*
* Example 5:
* Input: 1994
* Output: "MCMXCIV"
* Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
*
* */
public class IntegerToRoman {
class Solution {
public String intToRoman(int num) {
StringBuilder sb = new StringBuilder();
while (num > 0){
if(num >= 1000){
sb.append(convertNum(num/1000,"M","",""));
num = num % 1000;
}else if(num >= 100){
sb.append(convertNum(num/100,"C","D","M"));
num = num % 100;
}else if(num >= 10){
sb.append(convertNum(num/10,"X","L","C"));
num = num % 10;
}else{
sb.append(convertNum(num,"I","V","X"));
num = 0;
}
}
return sb.toString();
}
private String convertNum(int i,String one,String five,String ten){
StringBuilder sb = new StringBuilder();
if(i <= 3){
while (i > 0){
sb.append(one);
i--;
}
}else if(i == 4){
sb.append(one).append(five);
}else if(i == 9){
sb.append(one).append(ten);
}else{
sb.append(five);
i = i-5;
sb.append(convertNum(i,one,five,ten));
}
return sb.toString();
}
}
}