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leetcode-273-整数转换英文表示

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[题目链接]

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[题目描述]

将非负整数 num 转换为其对应的英文表示。

 

示例 1：

输入：num = 123
输出："One Hundred Twenty Three"

示例 2：

输入：num = 12345
输出："Twelve Thousand Three Hundred Forty Five"

示例 3：

输入：num = 1234567
输出："One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

示例 4：

输入：num = 1234567891
输出："One Billion Two Hundred Thirty Four Million Five Hundred Sixty Seven Thousand Eight Hundred Ninety One"

提示：

• 0 <= num <= $2^{31}$ - 1

思路一：英文水平

• 大家就当来复习英文水平就好了
• 因为这道题感觉真的没啥考察价值虽然是道hard
• 但是英文不行哪怕他是easy也做不出来
• 999为一组，然后注意特殊的证书1-20 其余的就没啥了
• 枚举拼接即可

class Solution {
    static String[] num2str_small = {
        "Zero", 
        "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", 
        "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"
    };
    static String[] num2str_medium = {
        "", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"
    };
    static String[] num2str_large = {
        "Billion", "Million", "Thousand", "",
    };
    String num2Str(int x) {
        String ans = "";
        if (x >= 100) {
            ans += num2str_small[x / 100] + " Hundred ";
            x %= 100;
        }
        if (x >= 20) {
            ans += num2str_medium[x / 10] + " ";
            x %= 10;
        }
        if (x != 0) ans += num2str_small[x] + " ";
        return ans;
    }
    public String numberToWords(int num) {
        if (num == 0) return num2str_small[0];
        StringBuilder sb = new StringBuilder();
        for (int i = (int)1e9, j = 0; i >= 1; i /= 1000, j++) {
            if (num < i) continue;
            sb.append(num2Str(num / i) + num2str_large[j] + " ");
            num %= i;
        }
        while (sb.charAt(sb.length() - 1) == ' ') sb.deleteCharAt(sb.length() - 1);
        return sb.toString();
    }
}

• ps:这里用的三叶大佬的代码，我写这种代码丑陋的过分，还是用三叶的看着舒服

• 时间复杂度O(n)

• 空间复杂度O(n)