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Commit 7e4abf0

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Add implementation for Majority Element using HashMap
1 parent bdbcdf2 commit 7e4abf0

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2 files changed

+194
-6
lines changed

2 files changed

+194
-6
lines changed

‎Hashing/HashMap/HashMapCode.java

Lines changed: 165 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,5 @@
1+
// the is written by chatgpt , all operation . In The Problem we use the inbuild HashMap.
2+
13

24
import java.util.LinkedList;
35

@@ -13,25 +15,182 @@ public Node(K key, V value) {
1315
}
1416
}
1517

16-
private int n;
17-
private int N;
18+
private int n;// n-> nodes
19+
private int N;// N-> buckets
1820
private LinkedList<Node> buckets[];
1921

2022
//constructor of HashMap
23+
@SuppressWarnings("unchecked")
2124
public HashMap(){
2225
this.N = 4;
2326
this.buckets = new LinkedList[4];
2427
for (int i = 0; i < N; i++) {
2528
this.buckets[i] = new LinkedList<>();
2629
}
2730
}
28-
public void put(K key, V value){
29-
31+
// Hash function to get bucket index
32+
private int hashFunction(K key) {
33+
int hc = key.hashCode();
34+
return Math.abs(hc) % N;
35+
}
36+
37+
// Search for a key in the bucket and return its index
38+
private int searchInLL(K key, int bi) {
39+
LinkedList<Node> ll = buckets[bi];
40+
int di = 0;
41+
for (int i = 0; i < ll.size(); i++) {
42+
Node node = ll.get(i);
43+
if (node.key.equals(key)) {
44+
return di;
45+
}
46+
di++;
47+
}
48+
return -1;
49+
}
50+
51+
// Rehash the HashMap when load factor exceeds threshold
52+
@SuppressWarnings("unchecked")
53+
private void rehash() {
54+
LinkedList<Node> oldBuckets[] = buckets;
55+
buckets = new LinkedList[N * 2];
56+
N = 2 * N;
57+
for (int i = 0; i < buckets.length; i++) {
58+
buckets[i] = new LinkedList<>();
59+
}
60+
61+
// Transfer all nodes to new buckets
62+
n = 0;
63+
for (int i = 0; i < oldBuckets.length; i++) {
64+
LinkedList<Node> ll = oldBuckets[i];
65+
for (int j = 0; j < ll.size(); j++) {
66+
Node node = ll.remove();
67+
put(node.key, node.value);
68+
}
69+
}
70+
}
71+
72+
// Put operation - Insert or update key-value pair
73+
public void put(K key, V value) {
74+
int bi = hashFunction(key);
75+
int di = searchInLL(key, bi);
76+
77+
if (di != -1) {
78+
// Key exists, update value
79+
Node node = buckets[bi].get(di);
80+
node.value = value;
81+
} else {
82+
// Key doesn't exist, add new node
83+
buckets[bi].add(new Node(key, value));
84+
n++;
85+
}
86+
87+
double lambda = (double) n / N;
88+
if (lambda > 2.0) {
89+
rehash();
90+
}
91+
}
92+
93+
// Check if key exists in HashMap
94+
public boolean containsKey(K key) {
95+
int bi = hashFunction(key);
96+
int di = searchInLL(key, bi);
97+
return di != -1;
98+
}
99+
100+
// Get value for a given key
101+
public V get(K key) {
102+
int bi = hashFunction(key);
103+
int di = searchInLL(key, bi);
104+
105+
if (di != -1) {
106+
Node node = buckets[bi].get(di);
107+
return node.value;
108+
} else {
109+
return null;
110+
}
111+
}
30112

113+
// Remove key-value pair from HashMap
114+
public V remove(K key) {
115+
int bi = hashFunction(key);
116+
int di = searchInLL(key, bi);
117+
118+
if (di != -1) {
119+
Node node = buckets[bi].remove(di);
120+
n--;
121+
return node.value;
122+
} else {
123+
return null;
124+
}
31125
}
32126

33-
public boolean containsKey(K key){
34-
return false;
127+
// Get all keys in the HashMap
128+
public java.util.ArrayList<K> keySet() {
129+
java.util.ArrayList<K> keys = new java.util.ArrayList<>();
130+
for (int i = 0; i < buckets.length; i++) {
131+
LinkedList<Node> ll = buckets[i];
132+
for (Node node : ll) {
133+
keys.add(node.key);
134+
}
135+
}
136+
return keys;
35137
}
138+
139+
// Check if HashMap is empty
140+
public boolean isEmpty() {
141+
return n == 0;
142+
}
143+
144+
// Get the size of HashMap
145+
public int size() {
146+
return n;
147+
}
148+
149+
// Print the HashMap for debugging
150+
public void printHashMap() {
151+
System.out.println("HashMap contents:");
152+
for (int i = 0; i < buckets.length; i++) {
153+
System.out.print("Bucket " + i + ": ");
154+
LinkedList<Node> ll = buckets[i];
155+
for (Node node : ll) {
156+
System.out.print("(" + node.key + "," + node.value + ") ");
157+
}
158+
System.out.println();
159+
}
160+
}
161+
}
162+
163+
// Main method for testing
164+
public static void main(String[] args) {
165+
HashMap<String, Integer> hm = new HashMap<>();
166+
167+
// Testing put operation
168+
hm.put("India", 100);
169+
hm.put("China", 150);
170+
hm.put("US", 50);
171+
hm.put("Nepal", 5);
172+
173+
System.out.println("Size: " + hm.size());
174+
hm.printHashMap();
175+
176+
// Testing get operation
177+
System.out.println("\nGet 'India': " + hm.get("India"));
178+
System.out.println("Get 'China': " + hm.get("China"));
179+
System.out.println("Get 'Pakistan': " + hm.get("Pakistan"));
180+
181+
// Testing containsKey operation
182+
System.out.println("\nContains 'India': " + hm.containsKey("India"));
183+
System.out.println("Contains 'Pakistan': " + hm.containsKey("Pakistan"));
184+
185+
// Testing remove operation
186+
System.out.println("\nRemoving 'China': " + hm.remove("China"));
187+
System.out.println("Size after removal: " + hm.size());
188+
hm.printHashMap();
189+
190+
// Testing keySet operation
191+
System.out.println("\nAll keys: " + hm.keySet());
192+
193+
// Testing isEmpty
194+
System.out.println("Is empty: " + hm.isEmpty());
36195
}
37196
}

‎Hashing/Question/MajorityElement.java

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
1+
2+
import java.util.HashMap;
3+
4+
public class MajorityElement {
5+
public static void main(String[] args) {
6+
int nums [] = {1,2,3,1,4,1,5,1,1,1,6,1};
7+
majority_element(nums);
8+
}
9+
10+
public static void majority_element(int num[]){
11+
HashMap <Integer,Integer> map = new HashMap<>();
12+
int size = num.length;
13+
14+
for(int i=0; i<size; i++){
15+
if(map.containsKey(num[i])){
16+
map.put(num[i],map.get(num[i])+1);
17+
}else{
18+
map.put(num[i],1);
19+
}
20+
21+
}
22+
for (int key : map.keySet()) {
23+
if(map.get(key) > size/3){
24+
System.out.println(key);
25+
}
26+
}
27+
28+
}
29+
}

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