FilesExpand file tree

 master

/

Huffman.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

158 lines (139 loc) · 5.06 KB

 master

/

Huffman.java

Copy path

Top

File metadata and controls

• Code
• Blame

158 lines (139 loc) · 5.06 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

import java.util.Comparator;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

import java.util.Scanner;

import java.util.Stack;

/**

*

* @author Mayank Kumar (mk9440)add

*/

/*

Output :

Enter number of distinct letters

6

Enter letters with its frequncy to encode

Enter letter : a

Enter frequncy : 45

Enter letter : b

Enter frequncy : 13

Enter letter : c

Enter frequncy : 12

Enter letter : d

Enter frequncy : 16

Enter letter : e

Enter frequncy : 9

Enter letter : f

Enter frequncy : 5

Letter Encoded Form

a 0

b 1 0 1

c 1 0 0

d 1 1 1

e 1 1 0 1

f 1 1 0 0

*/

class Node{

String letr="";

int freq=0,data=0;

Node left=null,right=null;

}

//A comparator class to sort list on the basis of their frequency

class comp implements Comparator<Node>{

@Override

public int compare(Node o1, Node o2) {

if(o1.freq>o2.freq){return 1;}

else if(o1.freq<o2.freq){return -1;}

else{return 0;}

}

}

public class Huffman {

// A simple function to print a given list

//I just made it for debugging

public static void print_list(List li){

Iterator<Node> it=li.iterator();

while(it.hasNext()){Node n=it.next();System.out.print(n.freq+" ");}System.out.println();

}

//Function for making tree (Huffman Tree)

public static Node make_huffmann_tree(List li){

//Sorting list in increasing order of its letter frequency

li.sort(new comp());

Node temp=null;

Iterator it=li.iterator();

//System.out.println(li.size());

//Loop for making huffman tree till only single node remains in list

while(true){

temp=new Node();

//a and b are Node which are to be combine to make its parent

Node a=new Node(),b=new Node();

a=null;b=null;

//checking if list is eligible for combining or not

//here first assignment of it.next in a will always be true as list till end will

//must have atleast one node

a=(Node)it.next();

//Below condition is to check either list has 2nd node or not to combine

//If this condition will be false, then it means construction of huffman tree is completed

if(it.hasNext()){b=(Node)it.next();}

//Combining first two smallest nodes in list to make its parent whose frequncy

//will be equals to sum of frequency of these two nodes

if(b!=null){

temp.freq=a.freq+b.freq;a.data=0;b.data=1;//assigining 0 and 1 to left and right nodes

temp.left=a;temp.right=b;

//after combing, removing first two nodes in list which are already combined

li.remove(0);//removes first element which is now combined -step1

li.remove(0);//removes 2nd element which comes on 1st position after deleting first in step1

li.add(temp);//adding new combined node to list

//print_list(li); //For visualizing each combination step

}

//Sorting after combining to again repeat above on sorted frequency list

li.sort(new comp());

it=li.iterator();//resetting list pointer to first node (head/root of tree)

if(li.size()==1){return (Node)it.next();} //base condition ,returning root of huffman tree

}

}

//Function for finding path between root and given letter ch

public static void dfs(Node n,String ch){

Stack<Node> st=new Stack(); // stack for storing path

int freq=n.freq; // recording root freq to avoid it adding in path encoding

find_path_and_encode(st,n,ch,freq);

}

//A simple utility function to print stack (Used for printing path)

public static void print_path(Stack<Node> st){

for(int i=0;i<st.size();i++){

System.out.print(st.elementAt(i).data+" ");

}

}

public static void find_path_and_encode(Stack<Node> st,Node root,String s,int f){

//Base condition

if(root!= null){

if(root.freq!=f){st.push(root);} // avoiding root to add in path/encoding bits

if(root.letr.equals(s)){print_path(st);return;} // Recursion stopping condition when path gets founded

find_path_and_encode(st,root.left,s,f);

find_path_and_encode(st,root.right,s,f);

//Popping if path not found in right or left of this node,because we previously

//pushed this node in taking a mindset that it might be in path

st.pop();

}

}

public static void main(String args[]){

List <Node> li=new LinkedList<>();

Scanner in=new Scanner(System.in);

System.out.println("Enter number of distinct letters ");

int n=in.nextInt();

String s[]=new String[n];

System.out.print("Enter letters with its frequncy to encode\n");

for(int i=0;i<n;i++){

Node a=new Node();

System.out.print("Enter letter : ");

a.letr=in.next();s[i]=a.letr;

System.out.print("Enter frequncy : ");

a.freq=in.nextInt();System.out.println();

li.add(a);

}

Node root=new Node();

root=make_huffmann_tree(li);

System.out.println("Letter\t\tEncoded Form");

for(int i=0;i<n;i++){

System.out.print(s[i]+"\t\t");dfs(root,s[i]);System.out.println();}

}

}