source.cpp

#include <unordered_map>
#include <vector>
#include <map>
#include <iostream>
#include <time.h>
std::vector<int> encoding(std::string s1) 
{ 
    std::cout << "Encoding\n"; 
    std::unordered_map<std::string, int> table; 
    for (int i = 0; i <= 255; i++) { 
        std::string ch = ""; 
        ch += char(i); 
        table[ch] = i; 
    } 
  
    std::string p = "", c = ""; 
    p += s1[0]; 
    int code = 256; 
    std::vector<int> output_code; 
    std::cout << "String\tOutput_Code\tAddition\n"; 
    for (int i = 0; i < s1.length(); i++) { 
        if (i != s1.length() - 1) 
            c += s1[i + 1]; 
        if (table.find(p + c) != table.end()) { 
            p = p + c; 
        } 
        else { 
            std::cout << p << "\t" << table[p] << "\t\t" 
                 << p + c << "\t" << code << std::endl; 
            output_code.push_back(table[p]); 
            table[p + c] = code; 
            code++; 
            p = c; 
        } 
        c = ""; 
    } 
    std::cout << p << "\t" << table[p] << std::endl; 
    output_code.push_back(table[p]); 
    return output_code; 
} 
  
void decoding(std::vector<int> op) 
{ 
    std::cout << "Decoding\n"; 
    std::unordered_map<int, std::string> table; 
    for (int i = 0; i <= 255; i++) { 
        std::string ch = ""; 
        ch += char(i); 
        table[i] = ch; 
    } 
    int old = op[0], n; 
    std::string s = table[old]; 
    std::string c = ""; 
    c += s[0]; 
    std::cout << s; 
    int count = 256; 
    for (int i = 0; i < op.size() - 1; i++) { 
        n = op[i + 1]; 
        if (table.find(n) == table.end()) { 
            s = table[old]; 
            s = s + c; 
        } 
        else { 
            s = table[n]; 
        } 
        std::cout << s; 
        c = ""; 
        c += s[0]; 
        table[count] = table[old] + c; 
        count++; 
        old = n; 
    }
    std::cout << "\nEND"<<std::endl;

} 
int main() 
{ 
    struct timespec start, stop;
    double time = 0;
    std::string s = "This is a hello message";
    if( clock_gettime(CLOCK_REALTIME, &start) == -1) { perror("clock gettime");} 
    std::vector<int> output_code = encoding(s); 
    if( clock_gettime( CLOCK_REALTIME, &stop) == -1 ) { perror("clock gettime");}       
    time = (stop.tv_sec - start.tv_sec)+ (double)(stop.tv_nsec - start.tv_nsec)/1e9;    
    std::cout << "Encoding time = " << time << " sec " <<std::endl; 
    std::cout << "Output Codes are: "; 
    for (int i = 0; i < output_code.size(); i++) { 
        std::cout << output_code[i] << " "; 
    } 
    std::cout << std::endl; 
    if( clock_gettime(CLOCK_REALTIME, &start) == -1) { perror("clock gettime");} 
    decoding(output_code); 
    if( clock_gettime( CLOCK_REALTIME, &stop) == -1 ) { perror("clock gettime");}  
    time = (stop.tv_sec - start.tv_sec)+ (double)(stop.tv_nsec - start.tv_nsec)/1e9;        
    std::cout << "Decoding time = " << time << " sec " <<std::endl; 
}