HJ42 学英语
描述
Jessi初学英语，为了快速读出一串数字，编写程序将数字转换成英文：
具体规则如下:
1.在英语读法中三位数字看成一整体，后面再加一个计数单位。从最右边往左数，三位一单位，例如12,345 等
2.每三位数后记得带上计数单位 分别是thousand, million, billion.
3.公式：百万以下千以上的数 X thousand X, 10亿以下百万以上的数：X million X thousand X, 10 亿以上的数：X billion X million X thousand X. 每个X分别代表三位数或两位数或一位数。
4.在英式英语中百位数和十位数之间要加and，美式英语中则会省略，我们这个题目采用加上and，百分位为零的话，这道题目我们省略and
下面再看几个数字例句：
22: twenty two
100: one hundred
145: one hundred and forty five
1,234: one thousand two hundred and thirty four
8,088: eight thousand (and) eighty eight (注:这个and可加可不加，这个题目我们选择不加)
486,669: four hundred and eighty six thousand six hundred and sixty nine
1,652,510: one million six hundred and fifty two thousand five hundred and ten
说明：
数字为正整数，不考虑小数，转化结果为英文小写；
保证输入的数据合法
关键字提示：and，billion，million，thousand，hundred。
数据范围：1 \le n \le 2000000 \1≤n≤2000000
输入描述：
输入一个long型整数
输出描述：
输出相应的英文写法
示例1
输入：
22
输出：
twenty two
#include<bits/stdc++.h>
using namespace std;
string num_20[] = {
"", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
"eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen", "twenty"};
string num_tens[] = {
"", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"};
string num_to_string(long long num){
string res;
long long x = num / 1000000000;
num = num % 1000000000;
if (x != 0){
res += num_to_string(x) + " billion ";
}
x = num / 1000000;
num = num % 1000000;
if (x != 0){
res += num_to_string(x) + " million ";
}
x = num / 1000;
num = num % 1000;
if (x != 0){
res += num_to_string(x) + " thousand ";
}
//
x = num / 100;
num = num % 100;
if (x != 0){
res += num_20[x] + " hundred ";
}
//
if (num > 0 && num <= 20){
if (x == 0) res += num_20[num] + " ";
else res += "and " + num_20[num] + " ";
}
if (num > 20){
if (x == 0) res += num_tens[num / 10] + " ";
else res += "and " + num_tens[num / 10] + " ";
if (num % 10 != 0) res += num_20[num % 10] + " ";
}
return res.substr(0, res.size()-1);
}
int main(){
long long num;
while(cin >> num){
cout << num_to_string(num);
}
return 0;
}