12. Go implementation of integer to Roman numeral and leetcode

12. Integer to Roman number

Roman numerals contain the following seven characters ： I, V, X, L,C,D  and  M.

character           The number
I             1
V             5
X             10
L             50
C             100
D             500
M             1000
for example , Rome digital 2 Write to do  II , Two parallel 1.12 Write to do  XII , That is to say  X + II . 27 Write to do   XXVII, That is to say  XX + V + II .

Usually , The small numbers in roman numbers are to the right of the big ones . But there are special cases , for example 4 Do not write  IIII, It is  IV. Numbers 1 In number 5 Left side , The number represented is equal to the large number 5 Decimal reduction 1 Value obtained 4 . similarly , Numbers 9 Expressed as  IX. This special rule only applies to the following six cases ：

I  Can be placed in  V (5) and  X (10) Left side , To express 4 and 9.
X  Can be placed in  L (50) and  C (100) Left side , To express 40 and  90. 
C  Can be placed in  D (500) and  M (1000) Left side , To express  400 and  900.
Give you an integer , Turn it into Roman numerals .

Example  1:

Input : num = 3
Output : "III"
Example  2:

Input : num = 4
Output : "IV"

Example  3:

Input : num = 9
Output : "IX"

Example  4:

Input : num = 58
Output : "LVIII"
explain : L = 50, V = 5, III = 3.

Example  5:

Input : num = 1994
Output : "MCMXCIV"
explain : M = 1000, CM = 900, XC = 90, IV = 4.

Tips ：

1 <= num <= 3999

Traverse ：

func intToRoman(num int) string {
    m := map[int]string{
        1:    "I",
		5:    "V",
		10:   "X",
		50:   "L",
		100:  "C",
		500:  "D",
		1000: "M",
    }
    m[4]="IV"
    m[9]="IX"
    m[40]="XL"
    m[90]="XC"
    m[400]="CD"
    m[900]="CM"
    arr := []int{1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1} 
    res:= ""
    for i:=0;i<len(arr);i++{
        if num==0 {
            break
        }
        val:=num/arr[i]
        for j:=0;j<val;j++{
            res = res + m[arr[i]]
        }
        num=num-val*arr[i]
    }
    return res
}

You can get from the prompt 1 <= num <= 3999, You can use enumeration , take num Enumerate the ten thousand bits of

func intToRoman(num int) string {
    res:=""
    ge := []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"} //0-9
    shi := []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"} //0-9
    bai := []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"} //0-9
    qian := []string{"", "M", "MM", "MMM"} //0-3
    res = qian[num/1000]+bai[num%1000/100]+shi[num%100/10]+ge[num%10]
    return res
}