add new solutions

solutions/1/q146/solution.go

@@ -0,0 +1,112 @@
+package q146
+
+type lruNode struct {
+	key, val   int
+	prev, next *lruNode
+}
+
+type LRUCache struct {
+	cap        int
+	index      map[int]*lruNode
+	head, tail *lruNode
+
+	nodes []lruNode
+	p     int
+}
+
+func Constructor(capacity int) LRUCache {
+	return LRUCache{
+		cap:   capacity,
+		index: make(map[int]*lruNode, capacity),
+		nodes: make([]lruNode, capacity),
+	}
+}
+
+func (c *LRUCache) alloc() *lruNode {
+	if c.p < len(c.nodes) {
+		c.p++
+		return &c.nodes[c.p-1]
+	}
+	return nil
+}
+
+func (c *LRUCache) touch(node *lruNode) {
+	if node.prev == nil {
+		return
+	}
+	if c.tail == node {
+		c.tail = node.prev
+	} else {
+		node.next.prev = node.prev
+	}
+	node.prev.next = node.next
+
+	node.prev = nil
+	node.next = c.head
+	c.head.prev = node
+	c.head = node
+}
+
+func (c *LRUCache) evict() *lruNode {
+	if len(c.index) < c.cap {
+		return nil
+	}
+
+	node := c.tail
+	delete(c.index, node.key)
+
+	if node.prev == nil {
+		c.head, c.tail = nil, nil
+	} else {
+		c.tail = node.prev
+		c.tail.next = nil
+	}
+	return node
+}
+
+func (c *LRUCache) Get(key int) int {
+	node := c.index[key]
+	if node == nil {
+		return -1
+	}
+	c.touch(node)
+	return node.val
+}
+
+func (c *LRUCache) Put(key int, value int) {
+	if c.cap == 0 {
+		return
+	}
+
+	node := c.index[key]
+	if node != nil {
+		node.val = value
+		c.touch(node)
+		return
+	}
+
+	node = c.alloc()
+	if node == nil {
+		node = c.evict()
+		*node = lruNode{} // clear
+	}
+
+	node.key, node.val = key, value
+	c.index[key] = node
+
+	node.next = c.head
+	if c.head != nil {
+		c.head.prev = node
+	}
+	c.head = node
+	if c.tail == nil {
+		c.tail = node
+	}
+}
+
+/**
+ * Your LRUCache object will be instantiated and called as such:
+ * obj := Constructor(capacity);
+ * param_1 := obj.Get(key);
+ * obj.Put(key,value);
+ */