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 <algorithm>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)

int n,r[]={5,3,3,3,3,3,4,3,4};
char c[][5]={{},{'.',',','!','?',' '},{'a','b','c'},{'d','e','f'},{'g','h','i'},{'j','k','l'},{'m','n','o'},{'p','q','r','s'},{'t','u','v'},{'w','x','y','z'}};
string s;

int main(){
	cin>>n;
	while(n--){
		cin>>s;
		int cur1=0,cur2=0;
		rep(i,s.size()){
			int m=s[i]-'0';
			if(!m){
				if(cur1){cout<<c[cur1][cur2];cur1=0;}
			}
			else{
				if(!cur1){cur1=m;cur2=0;}
				else cur2=(cur2+1)%r[cur1-1];
			}
		}
		cout<<endl;
	}
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<numeric>

using namespace std;

#define all(i) i.begin(), i.end()
#define rep(i,n) for(int i=0;i<n;i++)

int main()
{
	int num = 0; cin >> num;
	string dat[12] = { "", ".,!? ", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" };
	rep(i, num)
	{
		string str; cin >> str;
		vector<int> hit(10, 0);
		rep(j, (int)str.size())
		{
			hit[str[j] - '0'] += 1;
			if (j == 0 || str[j - 1] == '0') {}
			else if (str[j] == '0')
			{
				int tmp = str[j - 1] - '0', n = hit[tmp];
				while (1)
				{
					if (n <= (int)dat[tmp].size()) { break; }
					n -= (int)dat[tmp].size();
				}
				printf("%c", dat[tmp][n - 1]);
				rep(i, 10){ hit[i] = 0; }
			}
		}
		printf("\n");
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define fi first
#define se second
#define pb push_back
#define rep(i, s, n) for (int i = s; i < n; i++)
#define rrep(i, s, n) for (int i = (n)-1; i >= (s); i--)
#define all(a) a.begin(),a.end()
typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
const long long MOD = 1000000007, INF = 1e17;
 
#define endl '\n'
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0)
 
template<class T>inline bool chmax(T& a,T b){if(a<b){a=b;return true;}return false;}
template<class T>inline bool chmin(T& a,T b){if(a>b){a=b;return true;}return false;}

char c[] = {'a','d','g','j','m','p','t','w'};
char cc[] = {'.',',','!','?',' '};
int a[] = {3,3,3,3,3,4,3,4};

signed main()
{
	IOS();
	int N;
	cin>>N;
	vector<string>v;
	while(N--){
		string s;
		cin>>s;
		string t="";
		int flg = -1;
		rep(i,0,s.size()){
			if(s[i]=='0'){
				if(flg==-1)continue;
				if(s[i-1]=='1'){
					t+=cc[flg%5];
				}else{
					int tt = s[i-1]-'2';
					t+=c[tt]+flg%a[tt];
				}
				flg = -1;
			}else{
				flg++;
			}
		}
		v.push_back(t);
	}
	for(auto e:v){
		cout<<e<<endl;
	}
}

C++: #include <iostream>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <numeric>
#include <string>
#include <string.h>
#include <map>
#include <set>
#include <functional>
#include <complex>

using namespace std;

const int INF = (1<<30) - 1;

string table[] = {
    "",
    ",,!? ",
    "abc",
    "def",
    "ghi",
    "jkl",
    "mno",
    "pqrs",
    "tuv",
    "wxyz"
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int T;
    cin >> T;
    string in;
    while(T--){
        cin >> in;
        int i = 0;
        int n = in.length();
        
        while(i<n){
            int s = i;
            while(i<n && in[i]!='0'){
                i++;
            }
            if(0<i && in[i-1]-'0'!=0){
                string st = table[in[i-1]-'0'];
                cout << st[(i-s-1)%st.length()];
            }
            i++;
        }
        cout << endl;
    }
    
    return 0;
}

C++: #include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<cctype>
#include<complex>
#include<iostream>
#include<sstream>
#include<algorithm>
#include<functional>
#include<vector>
#include<string>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<bitset>
using namespace std;
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
#define INF 1e+8
#define EPS 1e-8
#define rep(i,j) for(int i = 0; i < (j); i++)
#define reps(i,j,k) for(int i = j; i < k; i++)
//typedef long long ll;
typedef pair<int,int> Pii;
int main(){
	int n;
	cin >> n;
	
	vector < string > change;
	change.push_back("");
	change.push_back(".,!? ");
	change.push_back("abc");
	change.push_back("def");
	change.push_back("ghi");
	change.push_back("jkl");
	change.push_back("mno");
	change.push_back("pqrs");
	change.push_back("tuv");
	change.push_back("wxyz");
	
	while(n--){
		string str;
		cin >> str;
		int len = str.size();
		string ans = "";
		rep(i,len){
			if(str[i] == '0')continue;
			int sub = i;
			while(str[i] == str[++sub]);
			if(str[sub-1]-48 == 1)ans += change[str[sub-1]-48][(sub-i-1)%5];
			else if(str[sub-1]-48 == 7 || str[sub-1]-48 == 9)ans += change[str[sub-1]-48][(sub-i-1)%4];
			else ans += change[str[sub-1]-48][(sub-i-1)%3];
			i = sub;
		}
		
		cout << ans << endl;
	}
	
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long   // <-----!!!!!!!!!!!!!!!!!!!

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define all(a) (a).begin(),(a).end()

typedef long long ll;
typedef pair<int, int> P;

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    vector<string> out{ "",
                        ".,!? ",
                        "abc",
                        "def",
                        "ghi",
                        "jkl",
                        "mno",
                        "pqrs",
                        "tuv",
                        "wxyz"};

    int n;
    cin >> n;
    while (n--) {
        string s;
        cin >> s;
        string ans = "";
        int base;
        int cnt = 0;
        rep(i, s.size()) {
            if (i >= 1 && s[i - 1] != '0' && s[i] == '0') {
                ans += out[base][(cnt - 1) % (int)out[base].size()];
                cnt = 0;
            } else if (s[i] != '0') {
                base = s[i] - '0';
                cnt++;
            }
        }

        cout << ans << endl;
        
    }

}