huffman coding using stl and without nodes c++

Question

the code has to print the huffman code for the characters in the string but it is giving wrong code for some characters (mostly for the chacters that get code 1 at the end

#include<iostream>
#include<string>
#include<map>
#include<queue>

using namespace std;

struct compare {
    bool operator()(pair<char, int> l, pair<char, int> r) {
        return r.second > l.second;
    }

};

map<char, int> frequencies(string str) {
    map<char, int> result;
    for (int i = 0; i < str.length(); i++) {
        if (result.find(str[i]) != result.end())
            result[str[i]]++;
        else
            result[str[i]] = 1;
    }
    return result;
}

void print(const map<char, int> a) {
    for (map<char, int>::const_iterator it = a.begin(); it != a.end(); it++) {
        cout << (it->first) << " " << (it->second) << endl;
    }

}

void prints(const map<char, string> a) {
    for (map<char, string>::const_iterator it = a.begin(); it != a.end(); it++) {
        cout << (it->first) << " " << (it->second) << endl;
    }

}

map<char, string> huffman(map<char, int> a) {
    priority_queue < pair < char, int >, vector < pair < char, int > >, compare > mappednodes;
    pair<char, int> root;
    pair<char, int> left, right;
    string s = "";
    map<char, string> result;

    for (map<char, int>::iterator itr = a.begin(); itr != a.end(); itr++) {
        mappednodes.push(pair<char, int>(itr->first, itr->second));
    }
    while (mappednodes.size() != 1) {
        left = mappednodes.top();
        mappednodes.pop();
        right = mappednodes.top();
        mappednodes.pop();
        root = make_pair('#', left.second + right.second);
        mappednodes.push(root);
        if (left.first != '#') {
            s = "0" + s;
            result[left.first] = s;
        }

        if (right.first != '#') {
            s = "1" + s;
            result[right.first] = s;
        }
    }
    return result;
}

int main() {
    string str;
    cout << "enter the string ";
    getline(cin, str);
    cout << endl;
    map<char, int> freq = frequencies(str);
    print(freq);
    cout << endl;
    map<char, string> codes = huffman(freq);
    prints(codes);


}

for example for string sasi it must give

s 0
i 10
a 11

but its giving

s 0
i 10
a 110

https://www.geeksforgeeks.org/huffman-coding-greedy-algo-3/

used this as basis but not getting anything

You have probably already used your debugger right? Which part seems to contain the bug? — Aykhan Hagverdili, Dec 09 '18 at 20:18
the last part of huffman trees logic has the error and havent used the debugger yet — Eswar Saladi, Dec 09 '18 at 20:25
If you have a code that behaves different than you expect, you should first debug before posting it here. In most cases you will find the problem yourself — Thomas Sablik, Dec 09 '18 at 20:28
checked it but the problem is with the last lines of code in huffman function where inserting into map is taking place — Eswar Saladi, Dec 09 '18 at 20:33
Did the debugging but I can't understand what to do with the problem in the logic — Eswar Saladi, Dec 09 '18 at 20:39
@user10605163 no it shouldnt come thats the problem with the code — Eswar Saladi, Dec 10 '18 at 13:37

score 0 · Answer 1 · answered Dec 10 '18 at 20:05

0

The problem is that you just keep adding characters ("bits") to s in the loop.

answered Dec 10 '18 at 20:05

Mark Adler

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huffman coding using stl and without nodes c++

1 Answers1