How should I practice Order Records by Matching Start and End?

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Problem · Hash Table

Order Records by Matching Start and End

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Problem statement

You are given a shuffled set of records. Record i has three fields: starts[i], ends[i], and payloads[i].

The records form exactly one chain. If record A has ends[A] == starts[B], then record A must appear immediately before record B in the chain.

Order the records by this chaining rule and concatenate their payloads in that order.

Function

concatenateOrderedPayloads(starts: String[], ends: String[], payloads: String[]) → String

Complete the function concatenateOrderedPayloads in the editor below.

concatenateOrderedPayloads has the following parameters:

String[] starts: the start keys
String[] ends: the end keys
String[] payloads: the payload fragments

Returns

String: the concatenated payload string after ordering the chain.

Examples

Example 1

starts = ["aaa", "bbb", "ccc"]ends = ["bbb", "ccc", "ddd"]payloads = ["2", "1", "3"]return = "213"

The only valid order is aaa -> bbb -> ccc -> ddd, so the payloads join as 2 + 1 + 3.

Example 2

starts = ["p"]ends = ["q"]payloads = ["X"]return = "X"

A single record is already ordered.

Constraints

1 <= starts.length == ends.length == payloads.length <= 2 * 10^5
The records form exactly one valid chain.