C++ :

#include<bits/stdc++.h>
using namespace std;
int h,m;
int main( ){
	string s[30] = {"zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen","twenty","thirty","forty","fifty"};
    cin>>h>>m;
    if(m == 0){
    	if(h <= 20){
    		cout<<s[h]<<" "<<"o'clock";
		}else{
			cout<<s[20]<<" "<<s[h % 10]<<" "<<"o'clock";
		}
	}else{
		if(h <= 20){
    		cout<<s[h]<<" ";
		}else{
			cout<<s[20]<<" "<<s[h % 10]<<" ";
		}
		if(m <= 20){
			cout<<s[m];
		}else{
			if(m > 20&&m < 30){
				cout<<s[20]<<" "<<s[m % 10];
			}else if(m >= 30&&m < 40){
				cout<<s[21]<<" "<<s[m % 10];
			}else if(m >= 40&&m < 50){
				cout<<s[22]<<" "<<s[m % 10];
			}else{
				cout<<s[23]<<" "<<s[m % 10];
			}
		}
	}
	
    return 0;
}

Java :

import java.util.Scanner;
public class Main {
    static int m;
    static int h;
    static String eng[]={"zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen","twenty","thirty","forty","fifty"};
    static String r=" o'clock";
    
    static void num_to_eng(int num){
        int a,b;
        a=num/10;
        b=num%10;
        if(num<=20)
            System.out.print(eng[num]);
        else
        {
            System.out.print(eng[a+18]);
            if(b!=0)
                System.out.print(" "+eng[b]);
        }
    }
    
    static void output(){
        if(m==0){
            num_to_eng(h);
            System.out.println(r);
            
        }
        else{
            num_to_eng(h);
            System.out.print(" ");
            num_to_eng(m);
            System.out.println();
        }
        
    }
    public static void main(String [] args){
        Scanner sc=new Scanner(System.in);
        h=sc.nextInt();
        m=sc.nextInt();
        output();
        
    }

}