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-rw-r--r--design_hashset.c108
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+// 705. Design HashSet
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/*
+ * design a 'HashSet' without using any built-in hash table libraries. implement
+ * 'MyHashSet' class:
+ * - 'void add(key)' inserts the value 'key' into the HashSet
+ * - 'bool contains(key)' returns whether the value 'key' exists or not
+ * - 'void remove(key)' removes the value 'key'. does nothing if 'key' does not
+ * exist
+ */
+
+#define TABLE_SIZE 500
+
+struct Node {
+ struct Node *next;
+ int val;
+};
+
+typedef struct {
+ struct Node *table[TABLE_SIZE];
+} MyHashSet;
+
+MyHashSet *myHashSetCreate() {
+ MyHashSet *obj = (MyHashSet *)malloc(sizeof(MyHashSet));
+ if (obj)
+ memset(obj, 0, sizeof(MyHashSet));
+ return obj;
+}
+
+void myHashSetAdd(MyHashSet *obj, int key) {
+ int idx = key % TABLE_SIZE;
+ struct Node **added_node;
+ struct Node *n = obj->table[idx];
+ if (!n)
+ added_node = &obj->table[idx];
+ else
+ while (n) {
+ if (n->val == key)
+ return;
+ if (!n->next) {
+ added_node = &n->next;
+ break;
+ }
+ n = n->next;
+ }
+ *added_node = (struct Node *)malloc(sizeof(struct Node));
+ (*added_node)->val = key;
+ (*added_node)->next = NULL;
+}
+
+void myHashSetRemove(MyHashSet *obj, int key) {
+ int idx = key % TABLE_SIZE;
+ struct Node *n = obj->table[idx], *t;
+ if (n && n->val == key) {
+ obj->table[idx] = n->next;
+ free(n);
+ } else {
+ while (n) {
+ if (n->next && n->next->val == key) {
+ t = n->next;
+ n->next = t->next;
+ free(t);
+ break;
+ }
+ n = n->next;
+ }
+ }
+}
+
+bool myHashSetContains(MyHashSet *obj, int key) {
+ int idx = key % TABLE_SIZE;
+ struct Node *n = obj->table[idx];
+ while (n) {
+ if (n->val == key)
+ return true;
+ n = n->next;
+ }
+ return false;
+}
+
+void myHashSetFree(MyHashSet *obj) {
+ struct Node *n, *t;
+ for (int i = 0; i < TABLE_SIZE; i++) {
+ n = obj->table[i];
+ while (n) {
+ t = n->next;
+ free(n);
+ n = t;
+ }
+ }
+ free(obj);
+}
+
+int main() {
+ MyHashSet *obj = myHashSetCreate();
+ myHashSetAdd(obj, 1);
+ myHashSetAdd(obj, 2);
+ printf("%d\n", myHashSetContains(obj, 1)); // expect: 1
+ printf("%d\n", myHashSetContains(obj, 3)); // expect: 0
+ myHashSetAdd(obj, 2);
+ printf("%d\n", myHashSetContains(obj, 2)); // expect: 1
+ myHashSetRemove(obj, 2);
+ printf("%d\n", myHashSetContains(obj, 2)); // expect: 0
+}