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Date: Mon, 11 Nov 1996 17:00:37 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Tue, 29 Oct 1996 21:21:14 GMTContent-length: 6598<html><head><title> Program 5 </title><center> <h2> Program 5 </h2> </center></head><body><ul><li> CS302 Section 12<li> TA: Michael Birk<li> <strong>Assigned:</strong> Tue 10/29/96<li> <strong>Due:</strong> Tue 11/5/96</ul>For this assignment you will write a program that can print a simplehistogram, or bar chart, based on the contents of a string. The chart showshow many of each letter of the alphabet appeared in the string. Forexample, when run on the string <tt>"Program Four"</tt>, the programshould print the following output:<p><pre> a: 1 * f: 1 * g: 1 * m: 1 * o: 2 ** p: 1 * r: 3 *** u: 1 * 11 letters scale factor: 1</pre><p>Note how only the letters are counted - punctuation, such as spaces, isignored. Also, upper- and lower- case letters are not distinguished. Thechart shows the number of occurrences of each letter in both numerical and"visual" form (a bunch of asterisks).<h2> How to Do It </h2>The basic technique is to create an array of integers to hold the counts foreach letter. The array should have 26 elements - one for each letter of thealphabet. The first element in the array will hold the number of A's, thesecond element holds the number of B's, and so on. You can achieve thismapping of the letters 'A' - 'Z' to the numbers 0 - 25 with the followingfunctions:<pre> int char_to_int (char ch) { return tolower (ch) - 'a'; } char int_to_char (int n) { return n + 'a'; }</pre>These functions rely on the fact that characters are really just integers,and the compiler will translate from one to the other automatically.<p>Your program should go through the entire input stringcharacter-by-character, and if it is a letter, add 1 to the count stored inthe element of the array that corresponds to that letter.<h2> What to Do </h2>There are some other requirements for this assignment. You must do these,but I highly recommend that you get the basics working first. Only work onthese after you can actually print out a simple histogram!<h3> Counting the Total Number of Characters </h3>You must count the total number of letters and print out this information. See the example below.<h3> Scaling the Bar Chart </h3>If any character occurs more than 50 times, you must scale all of the barsin the chart so that the longest bar is printed with 50 stars. You shouldalso print out the scaling factor. For example, if the input string was:<pre> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbb ccccccccccccccccccc d eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee fffffffffffff gggggg</pre>Then your program should print:<pre> a: 37 ***************** b: 22 ********** c: 19 ********* d: 1 e: 104 ************************************************** f: 13 ****** g: 6 ** 26 letters scale factor: 0.480769</pre>The scaling factor is just 1.0 if the most frequent character occurs at most50 times. If it appears, say 104 times, then the scaling factor would be50.0 / 104, or 0.480769. You would then multiply this scaling factor by thefrequency of each character to compute the number of stars to print.<h3> Using Functions </h3>Your program must be properly structured using functions. This means thatdifferent tasks or subproblems are performed in different functions. Information is passed in and out of the the functions via the parameters andreturn value.<p>To help push you in the right direction in this regard, I am instituting afew rules for this assignment.<p><ul> <li> No global variables may be used. All variables must be defined within a function definition. <li> No function may contain more than 15 statements (variable definitions, cin/cout, if, for, etc.) Most should have a lot fewer than that. If you're not sure if you're complying with this rule then ask me. <li> No function may contain more than one loop. (But of course it can call another function which has a loop.) <li> Only use simple counting loops (simple <tt>for</tt> loops).</ul><p>In addition, these rules always apply:<ul> <li> You must use proper indentation; indent the body of composite statements such as if, for, etc., and line up your curly braces! If you aren't sure then follow the book's guideline! <li> <b>All functions</b> must be documented using comments. These comments should explain what the function does and what the meanings of the parameters and return values are.</ul><h3> Reading the Input from a File </h3>Eventually, after you get everything else working, you must change yourprogram so that it get its input from a file. It should ask the user forthe name of the file, read the file, and use this as the input. Fortunately, this should be really easy, since I am providing you with afunction that reads an entire file as a single string. The function has thefollowing prototype:<pre> string read_file (string filename)</pre>This function reads the file <tt>filename</tt> and returns its contents asa single string. (This string may contain many lines, which are separatedby special newline and carriage return characters. Your program shouldjust ignore these, like all non-letters.) If there was an error (forexample, the file didn't exist) then it returns the empty string. <p>The read_file function is defined in the object file <a href="prog5/readfile.cpp">r:\public\mbirk\readfile.obj</a>. This meansthat you will have to add this to the Project Window. The Project Windowshould contain three files: <tt>prog4.cpp</tt>,<tt>r:\public\mbirk\string.obj</tt>, and<tt>r:\public\mbirk\readfile.obj</tt>.<h2> What to Hand In </h2>Hand in your source code, as well as the output of your program on thefollowing test cases: (note: don't hand in the test cases themselves)<p><ul> <li> <a href="prog5/test1.txt">Test 1</a> <li> <a href="prog5/test2.txt">Test 2</a></ul><p>Also, here are a couple more test cases and their result, which you canuse to see if your implementation is working. Do not hand these in.<p><ul> <li> <a href="prog5/test3.txt">Test 3</a> (<a href="prog5/test3out.txt">Output</a>) <li> <a href="prog5/test4.txt">Test 4</a> (<a href="prog5/test4out.txt">Output</a>)</ul><hr><i> <a href="mailto:mbirk@cs.wisc.edu">mbirk@cs.wisc.edu</a></body></html>⌨️ 快捷键说明
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