12. Integer to Roman

list的反转
Collections.sort(list, Collections.reverseOrder());

 

 

class Solution {
    public String intToRoman(int num) {
        HashMap<Integer, String> map = new HashMap<>();
        map.put(1, "I");
        map.put(4, "IV");
        map.put(5, "V");
        map.put(9, "IX");
        map.put(10, "X");
        map.put(40, "XL");
        map.put(50, "L");
        map.put(90, "XC");
        map.put(100, "C");
        map.put(400, "CD");
        map.put(500, "D");
        map.put(900, "CM");
        map.put(1000, "M");
        
        StringBuilder sb = new StringBuilder();
        List<Integer> integers = new ArrayList<Integer>(map.keySet());
        Collections.sort(integers, Collections.reverseOrder());
        for(int integer : integers) {
            int quotient = num / integer;
            for(int i = 0; i < quotient; i++) {
                sb.append(map.get(integer));
            }
            num = num % integer;
        }
        
        return sb.toString();
    }
}