MapReduce is a framework for large-scale data processing proposed by Google, and its open-source implementation, Hadoop MapReduce, is now widely used. Several language systems have been proposed to make developing MapReduce programs easier, for instance, Sawzall, FlumeJava, Pig, Hive, and Crunch. These language systems mainly target applications that can be naturally solved by using a MapReduce-like programming model. In this study, we propose a new MapReduce-program generator that accepts programs manipulating one-dimensional arrays. By using the proposed generator, users only need to write sequential programs to generate Hadoop MapReduce programs automatically. We applied some program optimization techniques to the generation of Hadoop MapReduce programs. In this paper, we also report our experiment results that compare programs generated by the proposed generator with hand-written MapReduce programs.