Create: 981-Time-Based-Key-Value-Store.ts

Author: andra961

Diff for: typescript/981-Time-Based-Key-Value-Store.ts

@@ -0,0 +1,44 @@
+//use an hashmap for keys, then each key will have an array (increasing order because of problem rules) of timestamps with values (represented as javascript objects {key, value})
+class TimeMap {
+    public hash: {};
+
+    constructor() {
+        this.hash = {};
+    }
+
+    set(key: string, value: string, timestamp: number): void {
+        if (key in this.hash) {
+            this.hash[key].push({ timestamp, value });
+        } else this.hash[key] = [{ timestamp, value }];
+    }
+
+    get(key: string, timestamp: number): string {
+        //if key is not in the hashmap there are no timestamps nor values, return ""
+        if (!(key in this.hash)) return '';
+        let timestamps = this.hash[key];
+        //if there are no timestamps or the first timestamp is already bigger than target timestamp(they are sorted so all next ones will big too), return ""
+        if (timestamps.length === 0 || timestamps[0].timestamp > timestamp)
+            return '';
+
+        //starts from the first timestamp as closest
+        let closest = timestamps[0];
+
+        let [l, r] = [0, timestamps.length - 1];
+
+        //binary search, but
+        while (l <= r) {
+            let mid = Math.floor((l + r) / 2);
+
+            if (timestamps[mid].timestamp === timestamp)
+                return timestamps[mid].value;
+            //update closest if mid element's timestamp is still less than target timestamp
+            if (timestamps[mid].timestamp < timestamp)
+                closest = timestamps[mid];
+
+            if (timestamps[mid].timestamp < timestamp) l = mid + 1;
+            if (timestamps[mid].timestamp > timestamp) r = mid - 1;
+        }
+
+        return closest.value;
+    }
+}