题解 | #学英语#

学英语

https://www.nowcoder.com/practice/1364723563ab43c99f3d38b5abef83bc

解题思路

首先需要处理1-19的基本数字到英文的映射
处理20,30,40...90这样的整十数到英文的映射
根据数字的位数，将其分成不同的部分：
- 个位数和十位数(1-99)
- 百位数(hundred)
- 千位数(thousand)
- 百万位(million)
从高位到低位处理，按照规则拼接英文单词
注意处理and的添加规则：百位后面有数字时需要加and

代码

python
java
cpp

def numberToWords(num):
    if num == 0:
        return "zero"
        
    ones = ["", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
            "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen",
            "seventeen", "eighteen", "nineteen"]
    tens = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
    
    def helper(n):
        if n == 0:
            return ""
        elif n < 20:
            return ones[n] + " "
        elif n < 100:
            return tens[n//10] + " " + ones[n%10] + " "
        elif n < 1000:
            if n % 100 == 0:
                return ones[n//100] + " hundred "
            return ones[n//100] + " hundred and " + helper(n%100)
        elif n < 1000000:
            if n % 1000 == 0:
                return helper(n//1000) + "thousand "
            return helper(n//1000) + "thousand " + helper(n%1000)
        else:
            if n % 1000000 == 0:
                return helper(n//1000000) + "million "
            return helper(n//1000000) + "million " + helper(n%1000000)
    ans = helper(num).strip()
    return ans.replace("  ", " ")

# 处理输入
n = int(input())
print(numberToWords(n))

import java.util.*;

public class Main {
    private final String[] ONES = {"", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
            "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
    private final String[] TENS = {"", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};

    public String numberToWords(int num) {
        if (num == 0) return "zero";
        return helper(num).trim();
    }

    private String helper(int num) {
        StringBuilder result = new StringBuilder();
        
        if (num >= 1000000) {
            result.append(helper(num / 1000000)).append("million ");
            num %= 1000000;
        }
        
        if (num >= 1000) {
            result.append(helper(num / 1000)).append("thousand ");
            num %= 1000;
        }
        
        if (num >= 100) {
            result.append(ONES[num / 100]).append(" hundred ");
            if (num % 100 != 0) {
                result.append("and ");
            }
            num %= 100;
        }
        
        if (num >= 20) {
            result.append(TENS[num / 10]).append(" ");
            if (num % 10 != 0) {
                result.append(ONES[num % 10]).append(" ");
            }
        } else if (num > 0) {
            result.append(ONES[num]).append(" ");
        }
        
        return result.toString();
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        System.out.println(new Main().numberToWords(n));
    }
}

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Solution {
private:
    vector<string> ones = {"", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
                          "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
    vector<string> tens = {"", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};
    
    string helper(int num) {
        if (num == 0) return "";
        
        string result;
        if (num >= 1000000) {
            result += helper(num / 1000000) + "million ";
            num %= 1000000;
        }
        
        if (num >= 1000) {
            result += helper(num / 1000) + "thousand ";
            num %= 1000;
        }
        
        if (num >= 100) {
            result += ones[num / 100] + " hundred ";
            if (num % 100 != 0) {
                result += "and ";
            }
            num %= 100;
        }
        
        if (num >= 20) {
            result += tens[num / 10] + " ";
            if (num % 10 != 0) {
                result += ones[num % 10] + " ";
            }
        } else if (num > 0) {
            result += ones[num] + " ";
        }
        
        return result;
    }
    
public:
    string numberToWords(int num) {
        if (num == 0) return "zero";
        string result = helper(num);
        // 删除末尾空格
        while (result.back() == ' ') {
            result.pop_back();
        }
        return result;
    }
};

int main() {
    int n;
    cin >> n;
    Solution solution;
    cout << solution.numberToWords(n) << endl;
    return 0;
}