#Leet Code# LRU Cache
语言：C++
描述：使用单链表实现，HeadNode是key=-1，value=-1，next=NULL的结点。距离HeadNode近的结点是使用频度最小的Node。
1 struct Node { 2 int key; 3 int value; 4 Node* next; 5 }; 6 7 class LRUCache { 8 public: 9 LRUCache(int capacity) { 10 this->capacity = capacity; 11 this->curLength = 0; 12 13 this->headNode = new Node(); 14 this->headNode->key = -1; 15 this->headNode->value = -1; 16 this->headNode->next = NULL; 17 18 this->lastNode = this->headNode; 19 } 20 21 int get(int key) { 22 if (this->curLength == 0) 23 return -1; 24 25 Node* tmpNode = reSequencing(key, -1); 26 if (tmpNode != NULL) { 27 return tmpNode->value; 28 } else { 29 return -1; 30 } 31 } 32 33 void set(int key, int value) { 34 if (this->capacity == 0) return; 35 36 Node* tmpNode = reSequencing(key, value); 37 if (tmpNode != NULL) { 38 tmpNode->value = value; 39 return; 40 } 41 42 if (this->curLength + 1 > this->capacity) { 43 if (this->headNode->next == this->lastNode) { 44 delete this->lastNode; 45 this->lastNode = this->headNode; 46 } else { 47 Node* t = this->headNode->next->next; 48 delete this->headNode->next; 49 this->headNode->next = t; 50 } 51 } 52 53 Node* newNode = new Node(); 54 newNode->key = key; 55 newNode->value = value; 56 newNode->next = NULL; 57 58 this->lastNode->next = newNode; 59 this->lastNode = newNode; 60 61 curLength += 1; 62 } 63 64 Node* reSequencing(int key, int value) { 65 Node* tmpNode = this->headNode; 66 Node* preNode; 67 68 while (tmpNode != NULL) { 69 if (tmpNode->key == key) { 70 break; 71 } 72 73 preNode = tmpNode; 74 tmpNode = tmpNode->next; 75 } 76 77 if (tmpNode != NULL && this->lastNode->key != key) { 78 preNode->next = tmpNode->next; 79 80 this->lastNode->next = tmpNode; 81 this->lastNode = tmpNode; 82 tmpNode->next = NULL; 83 } 84 85 return tmpNode; 86 } 87 88 private: 89 int capacity; 90 int curLength; 91 92 Node* headNode; 93 Node* lastNode; 94 };
