C :

#include <stdio.h>
int main()
{
    char c;
    while (scanf("%c",&c)==1)
    {
        if (c>=65 && c<=90) //A~Z
        {
            c+=33;
            if (c==123) c=97;
            printf("%c",c);
        } else
        if (c>=97 && c<=122)  //a~z
        {
            if (97<=c && c<=99)//abc
                printf("2");
            if (100<=c && c<=102)//def
                printf("3");
            if (103<=c && c<=105)//ghi
                printf("4");
            if (106<=c && c<=108)//jkl
                printf("5");
            if (109<=c && c<=111)//mno
                printf("6");
            if (112<=c && c<=115)//pqrs
                printf("7");
            if (116<=c && c<=118)//tuv
                printf("8");
            if (119<=c && c<=122)
                printf("9");
        }else printf("%c",c);
    }
    return 0;
}

C++ :

#include<bits/stdc++.h>
using namespace std;
string a;
int flag;
int main()
{
	while(cin>>a)
	{	
		for(int i=0;i<a.size();i++)
		{
			if(a[i]>='A'&&a[i]<='Z')
			{if(char(a[i]+32)=='z')cout<<'a';else cout<<char(a[i]+33);flag=1;}
			if(a[i]>='a'&&a[i]<='z')
			{
				if(a[i]>='a'&&a[i]<='c'){cout<<2;flag=1;}
				if(a[i]>='d'&&a[i]<='f'){cout<<3;flag=1;}
				if(a[i]>='g'&&a[i]<='i'){cout<<4;flag=1;}
				if(a[i]>='j'&&a[i]<='l'){cout<<5;flag=1;}
				if(a[i]>='m'&&a[i]<='o'){cout<<6;flag=1;}
				if(a[i]>='p'&&a[i]<='s'){cout<<7;flag=1;}
				if(a[i]>='t'&&a[i]<='v'){cout<<8;flag=1;}
				if(a[i]>='w'&&a[i]<='z'){cout<<9;flag=1;}
			}
			if(a[i]=='1'){cout<<1;flag=1;}
			if(a[i]=='0'){cout<<0;flag=1;}
			if(flag==0)cout<<a[i];
			flag=0;
		}
		cout<<endl;
	}
   return 0;
}
//zvbo941987
//YUANzi1987