[C++知识库]HJ21 简单密码（c++）

题目链接：简单密码_牛客题霸_牛客网

注意点：

1.switch语句

2.考虑哈希表的实现，推荐好：c++ map与unordered_map区别及使用_别说话写代码的博客-CSDN博客_unordered_map

3.小写字母转数字，推荐采用unordered_map来存放映射关系；

大写字母转小写，可以直接加32

4.isalpha()函数：C 库函数 – isalpha() | 菜鸟教程

方法一：

#include <iostream>
using namespace std;

int main()
{
	
	string str;
	while (cin >> str)
	{
		for(int i = 0; i < str.size(); ++i )
		{
			switch (str[i]) {
				case 'A'...'Y' : str[i] += 33; break;
				case 'Z' : str[i] = 'a' ;break;
				case 'a' ... 'c': str[i] = '2'; break;
            	case 'd' ... 'f': str[i] = '3'; break;
            	case 'g' ... 'i': str[i] = '4'; break;
            	case 'j' ... 'l': str[i] = '5'; break;
            	case 'm' ... 'o': str[i] = '6'; break;
            	case 'p' ... 's': str[i] = '7'; break;
            	case 't' ... 'v': str[i] = '8'; break;
            	case 'w' ... 'z': str[i] = '9'; break;
            	default: break;
			}
		
		}
		cout << str <<endl; 
	}
	return 0;
}

方法二：

#include <iostream>
#include <unordered_map>
#include <ctype.h>
using namespace std;

int main()
{
	unordered_map<char,char> m;
	m['a'] = m['b'] =m['c'] ='2';
	m['d'] = m['e'] = m['f'] ='3';
	m['g'] = m['h'] = m['i'] ='4';
	m['j'] = m['k'] = m['l'] ='5';
	m['m'] = m['n'] = m['o'] ='6';
	m['p'] = m['q'] = m['r'] = m['s'] ='7';
	m['t'] = m['u'] = m['v'] ='8';
	m['w'] = m['x'] = m['y'] = m['z'] = '9';
    m['Z'] = 'a';
	string str;
	while (cin >> str)
	{
		for(int i = 0; i < str.size(); ++i )
		{
			//两个条件的if不可以反 
			if(str[i] >= 'A' && str[i] < 'Z') 
			{
				str[i] = str[i] - 'A' + 'a' + 1;			
			}
			else if (isalpha(str[i])) 
			{
				str[i] = m[str[i]];	
			}	
		}
		cout << str <<endl; 
	}
	return 0;
}