杂谈记录——整数转罗马数字

一、贪心算法

列举各种可能

    int[] arr = {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"};
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稍加遍历即可

public String intToRoman(int num){
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < arr.length; i++) {
            int index = arr[i];
            while (num >= index){
                stringBuffer.append(symbols[i]);
                num -= index;
            }
        }
        return stringBuffer.toString();
    }
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二、硬编码

同样列举另外一种可能性

String[] thousands = {“”, “M”, “MM”, “MMM”};
String[] hundreds = {“”, “C”, “CC”, “CCC”, “CD”, “D”, “DC”, “DCC”, “DCCC”, “CM”};
String[] tens = {“”, “X”, “XX”, “XXX”, “XL”, “L”, “LX”, “LXX”, “LXXX”, “XC”};
String[] ones = {“”, “I”, “II”, “III”, “IV”, “V”, “VI”, “VII”, “VIII”, “IX”};

千位数字只能由 M 表示；
百位数字只能由 C，CD，D 和 CM 表示；
十位数字只能由 X，XL，L 和 XC 表示；
个位数字只能由 I，IV，V 和 IX 表示。

public String intToRoman(int num) {
        StringBuffer roman = new StringBuffer();
        roman.append(thousands[num / 1000]);
        roman.append(hundreds[num % 1000 / 100]);
        roman.append(tens[num % 100 / 10]);
        roman.append(ones[num % 10]);
        return roman.toString();
    }
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