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

typescript/981-Time-Based-Key-Value-Store.ts

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+//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;
+ }
+}