12. Integer to Roman Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. public class Solution { public String intToRoman(int num) { String[] oneLetters = {"I","X","C","M"}; String[] fiveLetters = {"V","L","D",""}; String numStr = num+""; String output = ""; for(int i=numStr.length()-1; i>=0; i--) { String tmp = ""; int bit = (int)num%(int)Math.pow(10,i+1)/(int)Math.pow(10,i); switch (bit){ case 1: tmp = oneLetters[i]; break; case 2: tmp = oneLetters[i]+oneLetters[i]; break; case 3: tmp = oneLetters[i]+oneLetters[i]+oneLetters[i]; break; case 4: tmp = oneLetters[i]+fiveLetters[i]; break; case 5: tmp = fiveLetters[i]; break; case 6: tmp = fiveLetters[i]+oneLetters[i]; break; case 7: tmp = fiveLetters[i]+oneLetters[i]+oneLetters[i]; break; case 8: tmp = fiveLetters[i]+oneLetters[i]+oneLetters[i]+oneLetters[i]; break; case 9: tmp = oneLetters[i]+oneLetters[i+1]; break; default: tmp = ""; break; } output += tmp; } return output; } } /////////////// //http://bangbingsyb.blogspot.com/2014/11/leetcode-integer-to-roman.html public class Solution { public String intToRoman(int num) { if(num <= 0) { return ""; } int[] nums = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}; String[] symbols = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}; StringBuilder res = new StringBuilder(); int digit=0; while (num > 0) { int times = num / nums[digit]; num -= nums[digit] * times; for ( ; times > 0; times--) { res.append(symbols[digit]); } digit++; } return res.toString(); } }