UMBC CMSC202, Computer Science II, Spring 1998, Sections 0101, 0102, 0103, 0104 and Honors

Tuesday February 10 1998

Assigned Reading:

• A Book on C: 6.7 - 6.9
• Programming Abstractions in C: 7.1 - 7.4

Handouts (available on-line): Introduction to Sorting, Sorting Routines.

Topics Covered:

• Using the assert() function. Program and sample run.

• Selection Sort

• Program to generate binary file of random integers. Note the use of the fstat() function to find the size of a file.

• Program and header file for some support routines to be used with our sorting routines.

• A makefile keeps everything up to date.

• Program to test Selection Sort and sample run. Note the use of "make -e" to turn off the debugging statements. It took over 5.2 hours to sort 400,000 integers.

• Insertion Sort can be somewhat faster than Selection Sort. Our test program and sample run show that it took only 3.2 hours to sort 400,000 integers.

• A graph of the running times of our experiments with Selection Sort and Insertion Sort show that the running times are proportional to n², where n is the number of items. By extending these curves we estimate that the running times to sort 1.6 million integers would take over 83 hours (about 3.5 days) and over 51 hours (about 2 days) for Selection Sort and Insertion Sort respectively.

• Merge Sort uses a divide-and-conquer strategy and solves the sorting problem by recursion. Our test program and sample runs show that Merge Sort takes only 23 seconds to sort 1.6 million items.