Explanation of the 2019 Kakao New Graduate Recruitment First Coding Test Problems

The 2019 Kakao New Graduate Recruitment First Online Coding Test was conducted on September 15 for 5 hours. Unlike the previous year, an efficiency test was introduced, changing the scoring method to allow partial points. Pass rates and solution strategies were released for problems primarily focused on implementation.

Key Problem Types and Solutions

• Open Chat Room: Utilizes an associative array (map) storing user IDs as keys and final nicknames as values to implement logic that batch-updates existing messages when nicknames are changed. The pass rate was 59.91%, the highest among the problems.
• Failure Rate: Calculates the ratio of users who reached but did not clear each stage to the number of users who reached it, then sorts in descending order. The pass rate was 55.57%.
• Matching Score: Extracts URLs and external links from HTML tags and sums the base score and link score based on the frequency of search terms. Regular expressions or string processing are key. The pass rate was 6.12%.
• Block Game: Implements a simulation where blocks are removed when dropping black blocks to complete a rectangle. An algorithm is required to traverse the board and find removable blocks. The pass rate was 5.85%.

Changes in Evaluation Criteria

This test introduced an efficiency test requiring efficient solutions based on input size. Consequently, even for the same problem, optimized code considering time complexity is necessary to achieve high scores, and a partial score system was applied to problems including the efficiency test.