Javascript 将阿拉伯数字转换成罗马数字

罗马数字真的很神奇

Examples: They wrote V instead of 5
And wrote IX instead of 9

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首先，了解罗马数字

阿拉伯数字	罗马数字
1	I
10	X
50	L
100	C
500	D
1000	M

其次，罗马数字的表示方法中的规则

1、
When a symbol appears after a larger symbol it is added
当一个符号左边大于右边时，两个符号相加表示数值大小
Example: VI = V + I = 5 + 1 = 6

2、
But if the symbol appears before a larger symbol it is subtracted
但是，当符号左边小于右边时，右边符号减去左边表示数值大小(10以内)
Example: IX = X - I = 10 - 1 = 9

3、
Don’t use the same symbol more than three times in a row (but IIII is sometimes used for 4, particularly on clocks)
不要将一个符号使用超过三次，在钟的表示里面例外

解题思路

第一步：将阿拉伯数字拆分开来，可以通过toString()方法(法二)，也可以通过下面的先取余后除的方法，按照数字从高位到低位的方法逐个将各位的数字获取出*（法一）*
第二步：构建一个二维数组，将各个位数可能出现的数值大小表示出来
第三步：将大象放进去
第四步：关上门

Javascript代码（法一）

function convert(num){
            if(isNaN(num)) return num;

            var a=[["","I","II","III","IV","V","VI","VII","VIII","IX"],
                          ["","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"],
                          ["","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"],["","M","MM","MMM"]];
            var roman = "";
            var t=0;
            for(var m = 0, i = 10000; m < 4; m++,i /= 10){
                t=Math.floor((num%i)/(i/10));
                roman += a[3-m][t];
            }
            return roman;
        }

convert(36);

Javascript代码（法二）

function convert(num){
            if(isNaN(num)) return num;

            var a=[["","I","II","III","IV","V","VI","VII","VIII","IX"],
                          ["","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"],
                          ["","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"],["","M","MM","MMM"]];
            var s = num.toString();
            var arr = [];
            var b = 0;
            for(var m = 0; m < s.length; m++){
              b=a[((s.length)-(m+1))][s[m]];//竟然忘了数组怎么用，卡了半天，真的难受233
              alert(b);
             arr.push(b);
            }
            b = arr.join("");
            return b;
        }

convert(36);

结语

真的还是要多练习，这么一个不是很复杂的题目看了将近三个小时，很难受香菇哈哈哈

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