Go: package main

import (
	"bytes"
	"fmt"
)

//Ktai has a keyboard and a state.
type Ktai struct {
	keyboard KeyBoard
	textBuf  *bytes.Buffer
}

// KeyBoard is type of a map.
type KeyBoard map[rune]string

// KEYBOARD that Ktai has
var KEYBOARD = KeyBoard{
	'0': "",
	'1': ".,!? ",
	'2': "abc",
	'3': "def",
	'4': "ghi",
	'5': "jkl",
	'6': "mno",
	'7': "pqrs",
	'8': "tuv",
	'9': "wxyz",
}

func main() {
	var N int
	fmt.Scanf("%d", &N)
	ktai := &Ktai{
		KEYBOARD, &bytes.Buffer{},
	}
	for i := 0; i < N; i++ {
		var numstr string
		fmt.Scanf("%s", &numstr)
		ktai.feed(numstr)
		ktai.print()
	}
}

func (ktai *Ktai) feed(str string) {
	var char *byte
	for _, v := range str {
		if v == '0' {
			if char != nil {
				ktai.textBuf.WriteByte(*char)
				char = nil
			}
			continue
		} else {
			runestring := ktai.keyboard[v]
			idx := ktai.indexOf(char, runestring)
			next := (idx + 1) % len(runestring)
			c := runestring[next]
			char = &c
		}
	}
}

func (ktai *Ktai) indexOf(ch *byte, str string) int {
	if ch == nil {
		return -1
	}
	r := rune(*ch)
	idx := -1
	for i, v := range str {
		if r == v {
			idx = i
			break
		}
	}
	return idx
}

func (ktai *Ktai) print() {
	fmt.Println(ktai.textBuf.String())
	ktai.textBuf.Reset()
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;
int main(){
  char m[9][5]={{'.',',','!','?',' '},
		{'a','b','c','1','1'},
		{'d','e','f','1','1'},
		{'g','h','i','1','1'},
		{'j','k','l','1','1'},
		{'m','n','o','1','1'},
		{'p','q','r','s','1'},
		{'t','u','v','1','1'},
		{'w','x','y','z','1'}};

  int a,count=0,c[100],d;
  char b[100000000000000][1025];
  cin>>a;
  for(int i=0;i<a;i++){
    scanf("%s",b[i]);
    c[i]=strlen(b[i]);
    for(int j=0;j<c[i];j++){
      if(b[i][j]!='0')count++;
      else
	if(b[i][j-1]!=0){
	  d=(int)(b[i][j-1])-48;

	  if(d==1)
	    if(count%5!=0)
	      cout<<m[d-1][count%5-1];
	    else cout<<m[d-1][4];

	  else if(d==7 || d==9)
	    if(count%4!=0)
	      cout<<m[d-1][count%4-1];
	    else cout<<m[d-1][3];

	  else
	    if(count%3!=0)
	      cout<<m[d-1][count%3-1];
	    else cout<<m[d-1][2]; 
	  count=0;
	}
    }
    cout<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(i64 (i) = (s);(i) < (e);(i)++)
#define all(x) x.begin(),x.end()
#define let auto const

int main() {
  vector<string> vec(10);
  vec[1] = ".,!? ";
  vec[2] = "abc";
  vec[3] = "def";
  vec[4] = "ghi";
  vec[5] = "jkl";
  vec[6] = "mno";
  vec[7] = "pqrs";
  vec[8] = "tuv";
  vec[9] = "wxyz";

  i64 n;
  cin >> n;
  rep(q, 0, n) {
    string s;
    cin >> s;
    i64 cnt = -1;
    string ans = "";
    rep(i,0,s.size()) {
      if(s[i] == '0') {
        if(cnt >= 0) {
          auto& v = vec[s[i - 1] + 1 - '1'];
          ans.push_back(v[cnt % v.size()]);
        }
        cnt = -1;
      }
      else {
        cnt++;
      }
    }
    cout << ans << endl;
  }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <cstdlib>

using std::cin;
using std::cout;
using std::endl;

char keitai[][6] =
{
	".,!? ",	
	"abc",
	"def",
	"ghi",
	"jkl",
	"mno",
	"pqrs",
	"tuv",
	"wxyz"
};

char out_keitai(int num, int count) {
	if (num == 1) {
		if (count%5 != 0) {
			return keitai[num-1][(count%5)-1];
		}else {
			return keitai[num-1][4];
		}
	}else if (num == 7 || num == 9) {
		if (count%4 != 0) {
			return keitai[num-1][(count%4)-1];
		}else {
			return keitai[num-1][3];
		}
	}else {
		if (count%3 != 0) {
			return keitai[num-1][(count%3)-1];
		}else {
			return keitai[num-1][2];
		}
	}
}
int main(void) {
	int n;
	char inp;
	std::string str;

	cin >> n;
	cin.ignore(2);

	for (int i = 0; i < n; i++) {
		getline(cin, str);
		int num;
		int count = 0;
		for (int j = 0; j < str.length(); j++) {
			std::string dstr;
			dstr = str.substr(j,1);
			num = atoi(dstr.c_str());
			if (num != 0) {
				count++;
				int seq = 1;
				int next_num;
				while (seq) {
					dstr = str.substr(j+1,1);
					next_num = atoi(dstr.c_str());
					if (num == next_num) {
						count++;
						j++;
					}else {
						seq = 0;
						cout << out_keitai(num,count);
						count = 0;
					}
				}	
			}
		}
		if (i != n-1) {
			cout << endl;
		}
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <numeric>
#include <algorithm>
using namespace std;
int n;

int main() {
    cin >> n;
    for(int i=0; i<n; ++i){
        string str; cin >> str;
        int N = str.size();
        for(int i=0; i<N; ++i){
            if(str[i]=='1'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%5==1) cout << ".";
                else if(cnt%5==2) cout << ",";
                else if(cnt%5==3) cout << "!";
                else if(cnt%5==4) cout << "?";
                else if(cnt%5==0) cout << " ";
            }else if(str[i]=='2'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "a";
                else if(cnt%3==2) cout << "b";
                else if(cnt%3==0) cout << "c";
            }else if(str[i]=='3'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "d";
                else if(cnt%3==2) cout << "e";
                else if(cnt%3==0) cout << "f";
            }else if(str[i]=='4'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "g";
                else if(cnt%3==2) cout << "h";
                else if(cnt%3==0) cout << "i";
            }else if(str[i]=='5'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "j";
                else if(cnt%3==2) cout << "k";
                else if(cnt%3==0) cout << "l";
            }else if(str[i]=='6'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "m";
                else if(cnt%3==2) cout << "n";
                else if(cnt%3==0) cout << "o";
            }else if(str[i]=='7'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%4==1) cout << "p";
                else if(cnt%4==2) cout << "q";
                else if(cnt%4==3) cout << "r";
                else if(cnt%4==0) cout << "s";
            }else if(str[i]=='8'){
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%3==1) cout << "t";
                else if(cnt%3==2) cout << "u";
                else if(cnt%3==0) cout << "v";
            }else{
                int pos = i, cnt=0;
                while(str[pos]!='0'){
                    pos++; cnt++;
                }
                i = pos;
                if(cnt%4==1) cout << "w";
                else if(cnt%4==2) cout << "x";
                else if(cnt%4==3) cout << "y";
                else if(cnt%4==0) cout << "z";
            }
        }
        cout << endl;
    }    
    return 0;
}