FilesExpand file tree

 master

/

HashMap.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

139 lines (118 loc) · 3.21 KB

 master

/

HashMap.java

Copy path

Top

File metadata and controls

• Code
• Blame

139 lines (118 loc) · 3.21 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

import java.util.ArrayList;

import java.util.LinkedList;

public class HashMap<K,V> {

public class hmnodes{ //HashMap nodes

K key;

V value;

}

private int size=0; //size of hashmap

private LinkedList<hmnodes> buckets[]; //array of addresses of list

public HashMap(){

buckets=new LinkedList[4]; //initially create bucket of any size

for(int i=0;i<4;i++)

buckets[i]=new LinkedList<>();

}

public void put(K key,V value) throws Exception{

int bi=bucketIndex(key); //find the index,the new key will be inserted in linklist at that index

int fountAt=find(bi,key); //check if key already exists or not

if(fountAt==-1){

hmnodes temp=new hmnodes(); //if doesn't exist create new node and insert

temp.key=key;

temp.value=value;

buckets[bi].addLast(temp);

this.size++;

}else{

buckets[bi].get(fountAt).value=value;//if already exist modify the value

}

double lambda = (this.size*1.0)/this.buckets.length;

if(lambda>2.0){

rehash(); //rehashing function which will increase the size of bucket as soon as lambda exceeds 2.0

}

return;

}

public V get(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return null;

}else{

return buckets[bi].get(fountAt).value;

}

}

public V remove(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return null;

}else{

this.size--;

return buckets[bi].remove(fountAt).value;

}

}

public boolean containskey(K key) throws Exception{

int bi=bucketIndex(key);

int fountAt=find(bi,key);

if(fountAt==-1){

return false;

}else{

return true;

}

}

public int size(){

return this.size;

}

public boolean isempty(){

return this.size==0;

}

public ArrayList<K> keyset() throws Exception{

ArrayList<K> arr=new ArrayList<>();

for(int i=0;i<buckets.length;i++){

for(int j=0;j<buckets[i].size();j++){

arr.add(buckets[i].get(j).key);

}

}

return arr;

}

public ArrayList<V> valueset() throws Exception{

ArrayList<V> arr=new ArrayList<>();

for(int i=0;i<buckets.length;i++){

for(int j=0;j<buckets[i].size();j++){

arr.add(buckets[i].get(j).value);

}

}

return arr;

}

public void display() throws Exception{

for(int i=0;i<buckets.length;i++){

System.out.print("Bucket: "+i+" ");

for(int j=0;j<buckets[i].size();j++){

hmnodes temp=buckets[i].get(j);

System.out.print("["+temp.key+"->"+temp.value+"]");

}

System.out.println();

}

}

public int find(int bi,K key) throws Exception{

for(int i=0;i<buckets[bi].size();i++){

if(key.equals(buckets[bi].get(i).key))

return i;

}

return -1;

}

public int bucketIndex(K key) throws Exception{

int bi=key.hashCode();

return Math.abs(bi%buckets.length);

}

private void rehash() throws Exception{

LinkedList<hmnodes> ob[]= buckets;

buckets=new LinkedList[ob.length*2];

for(int i=0;i<ob.length*2;i++)

buckets[i]=new LinkedList<>();

size = 0;

for(int i=0;i<ob.length;i++){

for(int j=0;j<ob[i].size();j++){

put(ob[i].get(j).key,ob[i].get(j).value);

}

}

}

}