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Parsons puzzles are popular for programming education. Identifying the strategies used by students solving Parsons puzzles is of interest because they can be used to determine to what extent students use the strategies typically associated with programming expertise, and to provide feedback and monitor the progress of students in a tutor. We propose solution sequence as an approximation of the student’s strategy for solving Parsons puzzles. It is scalable in terms of both the size of the puzzle and the number of students solving the puzzle. We propose BNF grammar to represent desirable puzzle-solving strategies associated with expert programmers. This representation is extensible and agnostic to the puzzle-solving strategies themselves. Finally, we propose a best match parser that matches a student’s solution sequence against the BNF grammar of a desirable strategy and quantifies the degree to which the student’s solution conforms to the desirable strategy. As a proof of concept, we used the parser to analyze the data collected by a Parsons puzzle tutor on if-else statements over five semesters and found a significant difference between C++ and Java puzzle-solvers in terms of their conformance to one desirable puzzle-solving strategy. Being able to tease out the effects of individual components of a strategy is one benefit of our approach: we found that relaxing shell-first constraint in the strategy resulted in significant improvement in the conformance of both C++ and Java students. 

In Parsons Puzzles, students are asked to arrange the lines of a program in their correct order. We investigated the effect of using mnemonic variable names in the program on the ease with which students solved the puzzles - whether students were able to solve puzzles containing mnemonic variable names with fewer actions or in less time than single-character variable names. We conducted a controlled study with cross-over design over four semesters. Much to our surprise, we found no statistically significant difference between students solving puzzles with mnemonic variable names versus single-character variable names - either in terms of the number of actions taken, the grade earned or the time spent per puzzle. In this paper, we will describe the experimental setup and data analysis and present the results of the study. We will discuss some hypotheses as to why the readability of the variable names did not impact students' ability to solve Parsons puzzles.