Create 146.cpp

LeetCode-CN/146.cpp

@@ -0,0 +1,89 @@
+#include <cstdlib>
+#include <cstring>
+#include <unordered_map>
+// DON'T USE STL LIST!! IT IS VERY SLOW!!!
+struct MyList
+{
+    int key, val;
+    MyList* pre;
+    MyList* next;
+};
+
+class LRUCache {
+public:
+    LRUCache(int capacity) {
+        maxsz = capacity;
+        sz = 0;
+        head = NULL;
+        end = NULL;
+    }
+
+    int get(int key) {
+        std::unordered_map<int, MyList*>::iterator iter = xp.find(key);
+        if (iter != xp.end())
+        {
+            MyList* tnode = iter->second;
+            if (tnode != head)
+            {
+                tnode->pre->next = tnode->next;
+                if (tnode->next)
+                {
+                    tnode->next->pre = tnode->pre;
+                }
+                else
+                {
+                    end = tnode->pre;
+                }
+                tnode->next = head;
+                tnode->pre = NULL;
+                head->pre = tnode;
+                head = tnode;
+            }
+            
+            return head->val;
+        }
+        else
+        {
+            return -1;
+        }
+    }
+
+    void put(int key, int value) {
+        if (get(key) != -1)
+        {
+            head->val = value;
+        }
+        else
+        {
+            MyList* xnode = (MyList*)malloc(sizeof(MyList));
+            xp.insert(std::make_pair(key, xnode));
+            xnode->key = key;
+            xnode->val = value;
+            xnode->pre = NULL;
+            xnode->next = head;
+            if(head) head->pre = xnode;
+            head = xnode;
+            if (end == NULL) end = head;
+
+            if (maxsz - sz)
+            {
+                sz++;
+            }
+            else
+            {
+                // keep sz 
+                xp.erase(end->key);
+                end = end->pre;
+                free(end->next);
+                end->next = NULL;
+            }
+        }
+    }
+private:
+    int maxsz;
+    int sz;
+    
+    std::unordered_map<int, MyList*> xp;
+    MyList* head;
+    MyList* end;
+};