leetcode Integer to Roman

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Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

罗马数字

1 5 10 50 100 500 1000

I V X L C D M

1~3 III

4 IV 是1，5

6～8 VI是5+几个1

9 是本位和高位的组合 9 IV， 90 XC， 900 CM

3999 / 3999 test cases passed.

Runtime: 388 ms

 string intToRoman(int num) {        char symbol[] = {'I', 'V', 'X', 'L', 'C', 'D', 'M'};        int scale = 1000;        int n = num;        string roman;                for (int i = 6; i >= 0; i -= 2) {            int digit = n / scale;            appToRoman(roman, digit, &symbol[i]);            n %= scale;            scale /= 10;        }                return roman;    }        void appToRoman(string &result, int num, char *symbol) {        if (0 == num) {            return;        } else if (num < 4) {            result.append(num, symbol[0]);        } else if (4 == num) {            result.append(1, symbol[0]);            result.append(1, symbol[1]);        } else if (num < 9) {            result.append(1, symbol[1]);            result.append(num - 5, symbol[0]);        } else {            result.append(1, symbol[0]);            result.append(1, symbol[2]);        }    }

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