LeetCode Java First 400 题解-012

最新推荐文章于 2019-11-20 13:08:55 发布

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#LeetCode #罗马数字

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本文介绍了一种将整数转换为罗马数字的算法实现，详细解释了罗马数字的构成规则，包括特殊情况的处理，如4和9的表示，并提供了一个Java函数示例，展示了如何通过数组存储罗马数字的每一种可能，以快速准确地进行转换。

Integer to Roman Medium

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol Value

I 1

V 5

X 10

L 50

C 100

D 500

M 1000

For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

I can be placed before V (5) and X (10) to make 4 and 9.
X can be placed before L (50) and C (100) to make 40 and 90.
C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.

Example 1:

Input: 3

Output: "III"

Example 2:

Input: 4

Output: "IV"

Example 3:

Input: 9

Output: "IX"

Example 4:

Input: 58

Output: "LVIII"

Explanation: C = 100, L = 50, XXX = 30 and III = 3.

Example 5:

Input: 1994

Output: "MCMXCIV"

Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

public String intToRoman(int num) {

    String M[] = {"", "M", "MM", "MMM"};

    String C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};

    String X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};

    String I[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};

    return M[num / 1000] + C[(num % 1000) / 100] + X[(num % 100) / 10] + I[num % 10];

}

思路：穷举每一位上所有数值的可能，然后将他们放入数组，0位置放空，通过取余+整除取出每一位的值连接即得结果。