本文迁移自老博客，原始链接为 https://seven.blog.ustc.edu.cn/usaconame-that-number/
读取一串数字，然后将数字翻译成与之映射的字母。由于一个数字映射多个字母，所以会产生多个字符串，将其中存在于dict.txt中的字符串输出。 解法：由于文件中共不到五千个字符串，所以可以反向的枚举。枚举文件中的所有字符串，若产生的数字和输入数字相同，则输出。
#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
ofstream fout ("namenum.out");
ifstream fin ("namenum.in");
ifstream fin1 ("dict.txt");
string str;
int len;
string num;
bool flag = false;
fin>>num;
while(fin1>>str)
{
string tmp;
len = str.size();
for(int i = 0; i < len; i++)
{
if((str[i] == 'A') || (str[i] == 'B') || (str[i] == 'C'))
{
tmp += "2";
}
else if((str[i] == 'D') || (str[i] == 'E') || (str[i] == 'F'))
{
tmp += "3";
}
else if((str[i] == 'G') || (str[i] == 'H') || (str[i] == 'I'))
{
tmp += "4";
}
else if((str[i] == 'J') || (str[i] == 'K') || (str[i] == 'L'))
{
tmp += "5";
}
else if((str[i] == 'M') || (str[i] == 'N') || (str[i] == 'O'))
{
tmp += "6";
}
else if((str[i] == 'P') || (str[i] == 'R') || (str[i] == 'S'))
{
tmp += "7";
}
else if((str[i] == 'T') || (str[i] == 'U') || (str[i] == 'V'))
{
tmp += "8";
}
else if((str[i] == 'W') || (str[i] == 'X') || (str[i] == 'Y'))
{
tmp += "9";
}
}
if(num == tmp)
{
fout<<str<<endl;
flag = true;
}
}
if(!flag)
fout<<"NONE"<<endl;
return 0;
}
