add 981

fishercoder1534 · fishercoder1534 · commit 96ab6f31d538 · 2020-11-23T10:11:38.000-08:00
diff --git a/README.md b/README.md
@@ -282,6 +282,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1003|[Check If Word Is Valid After Substitutions](https://leetcode.com/problems/check-if-word-is-valid-after-substitutions/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1003.java) | |Medium|
 |1002|[Find Common Characters](https://leetcode.com/problems/find-common-characters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1002.java) |  |Easy|
 |999|[Available Captures for Rook](https://leetcode.com/problems/available-captures-for-rook/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_999.java) | |Easy|
+|981|[Time Based Key-Value Store](https://leetcode.com/problems/time-based-key-value-store/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_981.java) | |Medium|
 |997|[Find the Town Judge](https://leetcode.com/problems/find-the-town-judge/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_997.java) | |Easy| 
 |994|[Rotting Oranges](https://leetcode.com/problems/rotting-oranges/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_994.java) | |Easy| BFS
 |993|[Cousins in Binary Tree](https://leetcode.com/problems/cousins-in-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_993.java) | |Easy| Tree, BFS
diff --git a/src/main/java/com/fishercoder/solutions/_981.java b/src/main/java/com/fishercoder/solutions/_981.java
@@ -0,0 +1,40 @@
+package com.fishercoder.solutions;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.TreeMap;
+
+public class _981 {
+    public static class Solution1 {
+
+        public static class TimeMap {
+
+            Map<String, TreeMap<Integer, String>> map;
+
+            /**
+             * Initialize your data structure here.
+             */
+            public TimeMap() {
+                this.map = new HashMap<>();
+            }
+
+            public void set(String key, String value, int timestamp) {
+                if (!map.containsKey(key)) {
+                    map.put(key, new TreeMap<>());
+                }
+                TreeMap<Integer, String> timestampMap = map.get(key);
+                timestampMap.put(timestamp, value);
+            }
+
+            public String get(String key, int timestamp) {
+                TreeMap<Integer, String> timestampMap = map.get(key);
+                Integer prevTimestamp = timestampMap.floorKey(timestamp);
+                if (prevTimestamp == null) {
+                    return "";
+                } else {
+                    return timestampMap.get(prevTimestamp);
+                }
+            }
+        }
+    }
+}
