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9f135d5 | 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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 | // LRU (Least Recently Used) Cache implementation
// Using hash table and doubly linked list for O(1) operations
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define CACHE_CAPACITY 1000
#define HASH_SIZE 2048
#define NUM_OPERATIONS 100000
typedef struct Node {
int key;
int value;
struct Node *prev;
struct Node *next;
} Node;
typedef struct {
Node **hash_table;
Node *head;
Node *tail;
int capacity;
int size;
} LRUCache;
Node* create_node(int key, int value) {
Node *node = (Node*)malloc(sizeof(Node));
node->key = key;
node->value = value;
node->prev = NULL;
node->next = NULL;
return node;
}
LRUCache* create_cache(int capacity) {
LRUCache *cache = (LRUCache*)malloc(sizeof(LRUCache));
cache->hash_table = (Node**)calloc(HASH_SIZE, sizeof(Node*));
cache->head = create_node(0, 0); // Dummy head
cache->tail = create_node(0, 0); // Dummy tail
cache->head->next = cache->tail;
cache->tail->prev = cache->head;
cache->capacity = capacity;
cache->size = 0;
return cache;
}
void move_to_front(LRUCache *cache, Node *node) {
// Remove from current position
node->prev->next = node->next;
node->next->prev = node->prev;
// Insert after head
node->next = cache->head->next;
node->prev = cache->head;
cache->head->next->prev = node;
cache->head->next = node;
}
int get(LRUCache *cache, int key) {
int hash = key % HASH_SIZE;
Node *node = cache->hash_table[hash];
// Search in hash bucket
while (node) {
if (node->key == key) {
move_to_front(cache, node);
return node->value;
}
node = node->next;
}
return -1; // Not found
}
void put(LRUCache *cache, int key, int value) {
int hash = key % HASH_SIZE;
// Check if key exists
Node *node = cache->hash_table[hash];
Node *prev = NULL;
while (node) {
if (node->key == key) {
node->value = value;
move_to_front(cache, node);
return;
}
prev = node;
node = node->next;
}
// Key doesn't exist - create new node
Node *new_node = create_node(key, value);
// Add to hash table
if (!cache->hash_table[hash]) {
cache->hash_table[hash] = new_node;
} else {
prev->next = new_node;
}
// Add to front of list
new_node->next = cache->head->next;
new_node->prev = cache->head;
cache->head->next->prev = new_node;
cache->head->next = new_node;
cache->size++;
// Evict if necessary
if (cache->size > cache->capacity) {
Node *lru = cache->tail->prev;
// Remove from list
lru->prev->next = cache->tail;
cache->tail->prev = lru->prev;
// Remove from hash table
int lru_hash = lru->key % HASH_SIZE;
Node *h = cache->hash_table[lru_hash];
Node *h_prev = NULL;
while (h) {
if (h->key == lru->key) {
if (h_prev) {
h_prev->next = h->next;
} else {
cache->hash_table[lru_hash] = h->next;
}
break;
}
h_prev = h;
h = h->next;
}
free(lru);
cache->size--;
}
}
int main() {
LRUCache *cache = create_cache(CACHE_CAPACITY);
unsigned int seed = 42;
clock_t start = clock();
int hits = 0, misses = 0;
for (int i = 0; i < NUM_OPERATIONS; i++) {
seed = seed * 1103515245 + 12345;
int operation = seed % 100;
seed = seed * 1103515245 + 12345;
int key = seed % (CACHE_CAPACITY * 2);
if (operation < 70) { // 70% puts
seed = seed * 1103515245 + 12345;
int value = seed % 10000;
put(cache, key, value);
} else { // 30% gets
int result = get(cache, key);
if (result != -1) {
hits++;
} else {
misses++;
}
}
}
clock_t end = clock();
double time_spent = (double)(end - start) / CLOCKS_PER_SEC;
printf("LRU Cache: capacity=%d, %d operations, %.6f seconds\n",
CACHE_CAPACITY, NUM_OPERATIONS, time_spent);
printf("Cache hits: %d, misses: %d, hit rate: %.2f%%\n",
hits, misses, 100.0 * hits / (hits + misses));
return 0;
}
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