add 706 design hashmap

Author: teckoo

_posts/coding/leetcode/2021-01-01-706-design-hashmap.md

@@ -0,0 +1,92 @@
+---
+layout: leetcode
+title: "706. Design HashMap"
+categories: [leetcode]
+---
+
+[Leetcode Link](https://leetcode.com/problems/design-hashmap/)
+
+Design a HashMap without using any built-in hash table libraries.
+
+Implement the MyHashMap class:
+
+* MyHashMap() initializes the object with an empty map.
+* void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.
+* int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
+* void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.
+ 
+```
+Example 1:
+
+Input
+["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
+[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
+Output
+[null, null, null, 1, -1, null, 1, null, -1]
+
+Explanation
+MyHashMap myHashMap = new MyHashMap();
+myHashMap.put(1, 1); // The map is now [[1,1]]
+myHashMap.put(2, 2); // The map is now [[1,1], [2,2]]
+myHashMap.get(1);    // return 1, The map is now [[1,1], [2,2]]
+myHashMap.get(3);    // return -1 (i.e., not found), The map is now [[1,1], [2,2]]
+myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (i.e., update the existing value)
+myHashMap.get(2);    // return 1, The map is now [[1,1], [2,1]]
+myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]]
+myHashMap.get(2);    // return -1 (i.e., not found), The map is now [[1,1]]
+ 
+
+Constraints:
+
+0 <= key, value <= 106
+At most 104 calls will be made to put, get, and remove.
+```
+
+# Solution
+
+```python
+  def __init__(self):
+      """
+      Initialize your data structure here.
+      """
+      self.cnt = 1000
+      self.bucket = [None] * self.cnt
+
+  def put(self, key: int, value: int) -> None:
+      """
+      value will always be non-negative.
+      """
+      idx = key % self.cnt
+      item = self.bucket[idx]
+      if item is None:
+          self.bucket[idx] = [[key, value]]
+      else:
+          for i in item:
+              if key == i[0]:
+                  i[1] = value
+                  return
+          item.append([key, value])
+
+  def get(self, key: int) -> int:
+      """
+      Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key
+      """
+      idx = key % self.cnt
+      item = self.bucket[idx]
+      if item:
+          for k, v in item:
+              if k == key: return v
+      return -1
+
+  def remove(self, key: int) -> None:
+      """
+      Removes the mapping of the specified value key if this map contains a mapping for the key
+      """
+      idx = key % self.cnt
+      item = self.bucket[idx]
+      if item:
+          for pos, i in enumerate(item):
+              if i[0] == key: 
+                  del item[pos]
+                  return
+```

media/js/tag-search-data.js

@@ -428,6 +428,14 @@ var problems = {
         templates: ["binary_search"],
         notes: "Simplest binary search, one item, l<=r",
     },
+    "706": {
+        name: "706. Design HashMap",
+        url: "/leetcode/706-design-hashmap",
+        tags: ["hashmap"],
+        keywords: ["lv_1"],
+        templates: [],
+        notes: "Use array or bucket for internal storage",
+    },
     "739": {
         name: "739. Daily Temperatures",
         url: "/leetcode/739-daily-temperatures",