Is Kth Distinct String in an Array easy or hard?

Kth Distinct String in an Array is categorized as an Easy problem. The main skill required is recognizing the frequency counting pattern with a hash map and preserving the original order of the array during the second pass.

Kth Distinct String in an Array Python/Java solution

In Python, use a dictionary or collections.Counter to track frequencies and iterate again to locate the kth string with count equal to one. In Java, use a HashMap for counting and a second loop through the array. Both implementations run in O(n) time and O(n) space.

How to solve Kth Distinct String in an Array in O(n)?

Use a dictionary or hash map to store the frequency of each string during the first traversal of the array. Then iterate through the array again and check which strings have a count of exactly one. Decrease k whenever you encounter such a string and return the string when k reaches zero.

What is the best approach for Kth Distinct String in an Array?

The best approach uses a hash map to count how many times each string appears, followed by a second pass through the array to find the kth string with frequency equal to one. This preserves the original order while keeping lookups constant time. The total complexity is O(n) time and O(n) space.

Is Kth Distinct String in an Array asked at Google/Amazon/Meta?

Frequency counting and order-preserving array problems are common in interviews at companies like Amazon, Google, and Meta. While this exact problem may appear more often on coding platforms, the underlying hash map counting pattern is widely used in real interview questions.

What data structure is used in Kth Distinct String in an Array?

A hash map (or dictionary) is the primary data structure used to store string frequencies. Some implementations also use sets to track strings seen once versus duplicates. These structures provide constant-time insert and lookup operations.

What is the time complexity of Kth Distinct String in an Array?

The optimal solution runs in O(n) time where n is the number of strings. One pass counts frequencies using a hash map and a second pass identifies the kth distinct string. Hash map operations are O(1) on average, keeping the overall complexity linear.

Description Hints 1 Solution Video 8:21

2053. Kth Distinct String in an Array

Easy82.1% acceptance2 companies

A distinct string is a string that is present only once in an array.

Given an array of strings arr, and an integer k, return the k^th distinct string present in arr. If there are fewer than k distinct strings, return an empty string "".

Note that the strings are considered in the order in which they appear in the array.

Example 1:

Input: arr = ["d","b","c","b","c","a"], k = 2
Output: "a"
Explanation:
The only distinct strings in arr are "d" and "a".
"d" appears 1^st, so it is the 1^st distinct string.
"a" appears 2^nd, so it is the 2^nd distinct string.
Since k == 2, "a" is returned.

Example 2:

Input: arr = ["aaa","aa","a"], k = 1
Output: "aaa"
Explanation:
All strings in arr are distinct, so the 1^st string "aaa" is returned.

Example 3:

Input: arr = ["a","b","a"], k = 3
Output: ""
Explanation:
The only distinct string is "b". Since there are fewer than 3 distinct strings, we return an empty string "".

Constraints: