Yahoo OA Full Analysis｜Yahoo OA Interview Process + High Frequency Question Types [With Preparation Advice].

In recent years, Yahoo is no longer a hot Internet giant, but it still has a stable user base in search, finance, media, and other areas, and it continues to recruit talented engineering and data professionals around the world. In particular Yahoo! SDE Newcomer and Intern positions attract a lot of applicants every year, and the online written test is the first step to get started. We have compiled two representative questions from the 2025 Yahoo OA, covering typical string algorithms and greedy strategies, which are considered to be "moderately difficult" in the actual test, and are suitable for those who are preparing for the FAANG written test of the same level to practice. Below are the full questions, the explanation ideas and experience sharing.

Question 1. Count Binary Substrings

Problem Description

You are given a binary string s containing only characters '0' and '1'. Your task is to count the number of non-empty substrings that have the following properties.

1. The number of 0s and 1s in the substring are equal.
2. All the 0s and all the 1s in the substring are grouped consecutively(SIGHS) That is, it must look like '000111' or '11', but not '0101'.

Note that substrings can overlap, and duplicates should be counted.

Example.

Input: s = "011001"
Output: 4
Explanation: Valid substrings are "01", "10", "1100", and "01" (at the end).

Question 2. Remove Duplicates for Lexicographically Largest Result

Problem Description

You're given a string input_str You may remove any duplicate character to make the string consist of unique characters only.

Your goal is to return the lexicographically largest possible result string after such removals.

You may perform the removals in any order, and must ensure that each character appears at most once in the final output.

Example.

Input: input_str = "aabcb"
Output: "acb"
Explanation.
We remove the first 'a' and the first 'b'. Among all strings with unique characters, "acb" is lexicographically the largest.

Practical experience sharing｜Yahoo OA Rhythm of work

This time, when the students we coached took Yahoo OA, the feedback was that the overall interface was in the HackerRank style, the test time was about 90 minutes, and both questions needed to write their own function bodies, and the programming language supported mainstream languages such as Java / Python / C++. Although the questions themselves are not very difficult, they require strong ability to deal with details, otherwise it is easy to lose points on boundary cases.

Although the topic does not emphasize the time complexity requirement, it spells out optimization details in the final 10% submitter, and it is recommended to write O(n) methods directly in the exercise to ensure that you can AC all test cases.

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