Update README.md

README.md

@@ -1 +1,18 @@
-# Day1
+# Day1
+
+#Problem 1:
+Design a HashMap without using any built-in hash table libraries.
+To be specific, your design should include these functions: Follow up: How would you handle collisions in HashMap?
+put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
+get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
+remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.
+
+#Problem 2:
+Design a Data Structure SpecialStack that supports all the stack operations like push(), pop(), isEmpty(), isFull() and an additional operation getMin() which should return minimum element from the SpecialStack. All these operations of SpecialStack must be O(1). To implement SpecialStack, you should only use standard Stack data structure and no other data structure like arrays, list, .. etc. 
+
+#Problem 3:
+Design a HashSet without using any built-in hash table libraries.
+To be specific, your design should include these functions:
+add(value): Insert a value into the HashSet. 
+contains(value) : Return whether the value exists in the HashSet or not.
+remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.