Merge branch 'master' of https://github.com/sundeshgupta/encoding-algorithm

merging master

Author: sundeshgupta

improved-huffman.cpp

@@ -0,0 +1,141 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+struct pixel{
+	int freq;
+	int label;
+	pixel* left, *right;
+
+	pixel(int x, int y):	label(x), freq(y){
+		left = NULL;
+		right = NULL;
+	}
+
+	void print(){
+		cout << label << " " << freq << endl;
+	}
+};
+
+struct huffcode{
+	int label;
+	int parent;
+	string code;
+};
+
+struct compare{
+	bool operator() (pixel* a, pixel* b){
+		return a->freq > b->freq;
+	}
+};
+
+ofstream out("huffman.txt");
+
+huffcode codes[256];
+
+void preoder(pixel* root, string s, int level, int parent){
+	
+	if(root->label < 256){
+		// if(level >= 3){
+		// 	codes[root->label].parent = parent;
+		// }
+		// else{
+		// 	codes[root->label].parent = -1;
+		// }
+		codes[root->label].parent = parent;
+		codes[root->label].code = s;
+		cout << setfill(' ') << setw(3) << root->label 
+			<< " -> " << setw(7) << s << setw(4) << codes[root->label].parent<< endl; 
+		return;
+	}
+
+	out << root->label << " -> " << root->left->label << " [ label = \"" << s+'0' << "\"];"<<endl;
+	out << root->label << " -> " << root->right->label << " [ label = \"" << s+'1' << "\"];" << endl; 
+	
+	if(level == 3)
+		parent = root->label;
+
+	preoder(root->left , s + '0', level+1, parent);
+	preoder(root->right, s + '1', level+1, parent);
+
+	return;
+}
+
+int main(){
+
+	// Uploading Image
+
+	string s;
+	cin >> s;
+
+	int freq[256] = {0};
+
+	for(auto i: s){
+		freq[i] += 1;
+	}
+
+	priority_queue<pixel*, vector<pixel*>, compare> pq;
+
+	for(int i = 0; i < 256; i++){
+		if (freq[i] > 0){
+			pixel* tmp = new pixel(i, freq[i]);
+			pq.push(tmp);
+		}
+	}
+
+	int cnt = 256;
+
+	while(pq.size() > 1){
+		pixel* first = pq.top();
+		pq.pop();
+		pixel* second = pq.top();
+		pq.pop();
+		pixel* tmp = new pixel(cnt++, first->freq + second->freq);
+		tmp->left = first;
+		tmp->right = second;
+		pq.push(tmp);
+	}
+
+	pixel* root = pq.top();
+
+	out << "digraph{" << endl;
+
+	preoder(root, "", 0 , -1);
+	
+	out << "}" << endl;
+
+	// string str = "dot -Tpng huffman.txt -o huffman.png";	// running dot file through terminal
+	// const char *command = str.c_str();					// system function is copied from https://www.geeksforgeeks.org/system-call-in-c/
+	// system(command);
+
+
+	string w;
+	int last = -1;
+	bool f = 0;
+
+	for(int i = 0; i < s.length(); i++){
+		if(f == 0){
+			w += codes[s[i]].code;
+		}
+		else if(codes[s[i]].parent == codes[last].parent){
+			w += '1';
+			string code = codes[s[i]].code;
+			w += code.substr(3, code.length());
+		}
+		else{
+			w += '0';
+			w += codes[s[i]].code;
+		}
+		if(codes[s[i]].parent == -1)
+			f = 0;
+		else{
+			last = s[i];
+			f = 1;
+		}
+	}
+
+	cout << w << endl;
+	cout << w.length() << " " << s.length() * 4 << endl;
+
+	return 0;
+}