LeetCode: LRU Cache

看别人的答案：

 1 struct CacheNode {
 2     int key, value;
 3     CacheNode(int a, int b) : key(a), value(b) { }
 4 };
 5 class LRUCache{
 6 public:
 7     LRUCache(int capacity) {
 8         size = capacity;
 9     }
10     
11     int get(int key) {
12         if (cacheMap.find(key) == cacheMap.end()) return -1;
13         else {
14             cachelist.splice(cachelist.begin(), cachelist, cacheMap[key]);
15             cacheMap[key] = cachelist.begin();
16             return cacheMap[key]->value;
17         }
18     }
19     
20     void set(int key, int value) {
21         if (cacheMap.find(key) == cacheMap.end()) {
22             if (cachelist.size() == size) {
23                 cacheMap.erase(cachelist.back().key);
24                 cachelist.pop_back();
25             }
26             cachelist.push_front(CacheNode(key, value));
27             cacheMap[key] = cachelist.begin();
28         }
29         else {
30             cacheMap[key]->value = value;
31             cachelist.splice(cachelist.begin(), cachelist, cacheMap[key]);
32             cacheMap[key] = cachelist.begin();
33         }
34     }
35     
36 private:
37     list<CacheNode> cachelist;
38     unordered_map<int, list<CacheNode>::iterator> cacheMap;
39     int size;
40 };

自己写了另一段更容易懂的代码：

 1 struct node {
 2     int key;
 3     int val;
 4     node* next;
 5     node(int k, int v) : key(k), val(v), next(NULL) { }
 6 };
 7 class LRUCache{
 8 public:
 9     LRUCache(int capacity) {
10         len = capacity;
11     }
12     
13     int get(int key) {
14         if (!head) return -1;
15         if (head->key == key) return head->val;
16         node* p = head;
17         int cur = 1;
18         while (p->next && cur < len) {
19             cur++;
20             if (p->next->key == key) {
21                 node* q = p->next;;
22                 p->next = p->next->next;
23                 q->next = head;
24                 head = q;
25                 return head->val;
26             }
27             p = p->next;
28         }
29         return -1;
30     }
31     
32     void set(int key, int value) {
33         if (!head) head = new node(key, value);
34         else {
35             node* p = new node(key, value);
36             p->next = head;
37             head = p;
38             int cur = 1;
39             while (p->next && cur < len) {
40                 cur++;
41                 if (p->next->key == key) {
42                     p->next = p->next->next;
43                     break;
44                 }
45                 p = p->next;
46             }
47         }
48     }
49 private:
50     node* head = NULL;
51     int len;
52 };

 1 public class node {
 2     public int key;
 3     public int val;
 4     public node next;
 5     public node(int k, int v) {
 6         key = k;
 7         val = v;
 8         next = null;
 9     }
10 };
11 public class LRUCache {
12 
13     public LRUCache(int capacity) {
14         head = null;
15         len = capacity;
16     }
17 
18     public int Get(int key) {
19         if (head == null) return -1;
20         if (head.key == key) return head.val;
21         node p = head;
22         int cur = 1;
23         while (p.next != null && cur < len) {
24             cur++;
25             if (p.next.key == key) {
26                 node q = p.next;
27                 p.next = p.next.next;
28                 q.next = head;
29                 head = q;
30                 return head.val;
31             }
32             p = p.next;
33         }
34         return -1;
35     }
36 
37     public void Set(int key, int value) {
38         if (head == null) head = new node(key, value);
39         else {
40             node p = new node(key, value);
41             p.next = head;
42             head = p;
43             int cur = 1;
44             while (p.next != null && cur < len) {
45                 cur++;
46                 if (p.next.key == key) {
47                     p.next = p.next.next;
48                     break;
49                 }
50                 p = p.next;
51             }
52         }
53     }
54     node head;
55     int len;
56 }

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posted @ 2014-01-09 08:46 ying_vincent 阅读(169) 评论(0) 收藏举报

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