Integer to Roman(整型转为罗马数)leetcode12

Myth丶恋晨 2022-05-24 03:48 176阅读 0赞

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.

code1：（暴力一点的）

public String intToRoman(int num) {
            String[] res=new String[Integer.toString(num).length()];
            int bit=0;
            int index=0;
            while(num!=0){
                int i=num%10;
                num=num/10;
                bit++;
                res[index]="";
                if(bit==1){
                    if(i<4){
                        for(int j=0;j<i;j++)
                            res[index]+="I";
                    }else if(i==4){
                        res[index]="IV";
                    }else if(i==9){
                        res[index]="IX";
                    }
                    else{
                        res[index]="V";
                        for(int j=0;j<i-5;j++){
                            res[index]+="I";
                        }
                    }
                }else if(bit==2){
                     if(i<4){
                        for(int j=0;j<i;j++)
                            res[index]+="X";
                    }else if(i==4){
                        res[index]="XL";
                    }else if(i==9){
                        res[index]="XC"; 
                     }else{
                        res[index]="L";
                        for(int j=0;j<i-5;j++){
                            res[index]+="X";
                        }
                    }
                    
                }else if(bit==3){
                      if(i<4){
                        for(int j=0;j<i;j++)
                            res[index]+="C";
                    }else if(i==4){
                        res[index]="CD";
                    }else if(i==9){
                        res[index]="CM"; 
                     }else{
                        res[index]="D";
                        for(int j=0;j<i-5;j++){
                            res[index]+="C";
                        }
                    }
                }else{
                       if(i<4){
                        for(int j=0;j<i;j++)
                            res[index]+="M";
                    }
                }
                index++;
            }
            StringBuilder result=new StringBuilder();
            for(int i=res.length-1;i>=0;i--){
                result.append(res[i]);
            }
            return result.toString();
    }

code2：（别人家的优雅的）

public String intToRoman(int num) {
            String[] romans={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
            int[] nums={1000,900,500,400,100,90,50,40,10,9,5,4,1};
            StringBuilder sb=new StringBuilder();
            for(int i=0;i<nums.length;i++){
                int count=num/nums[i];
                while(count!=0){
                    sb.append(romans[i]);
                    count--;
                }
                num=num%nums[i];
            }
            return sb.toString();
        }