ch1/13.c

   1 /*
   2  * Example 1-13:
   3  * Write a program to print a histogram of the lengths of words in its input.
   4  * It is easy to draw the histogram with the bars horizontal;
   5  * a vertical orientation is more challenging.
   6  */
   7
   8 /*
   9  * NOTE: Word separator tokens are isspace() and EOF.
  10  *
  11  * TODO: Split giant main() into functions?
  12  *       Make output graph even more flexible
  13  *       Eliminate all fixed graph output
  14  *       Support MAX_CHARS > 100
  15  *       Prove working (unit tests?)
  16  */
  17
  18 #include <stdlib.h>
  19 #include <stdio.h>
  20 #include <ctype.h>       /* for isspace() */
  21
  22 #define MAX_CHARS 10     /* [< 100] longer words placed in separate column */
  23 #define BAR_CHAR  '*'    /* char used in bars */
  24 #define BAR_SEP   "  "   /* spaces between bars */
  25
  26 int
  27 main(void)
  28 {
  29         /*
  30          * Occurance freqs of n-character words - words[n].
  31          * words[MAX_CHARS+1] is for words > MAX_CHARS.
  32          * Init all indices to 0.
  33          */
  34         int words[MAX_CHARS+1] = {0};
  35
  36         /*
  37          * Read input: Count char num in each word (n); store as words[n-1].
  38          * Record last char as lastchar, only needed to check for newline.
  39          */
  40         int lastchar = EOF;     /* last input char */
  41         int chars = 0;          /* chars in each word */
  42         int c;
  43         while ( (c = getchar()) ) {
  44                 if (!isspace(c) && c != EOF)
  45                         ++chars;
  46                 else {
  47                         // End of word/file; bump freq for last word's length.
  48                         if (chars <= MAX_CHARS)
  49                                 ++words[chars-1];
  50                         else
  51                                 ++words[MAX_CHARS];    /* long word, last col */
  52
  53                         if (EOF == c)
  54                                 break;
  55                         chars = 0;        /* prep for next word */
  56                         lastchar = c;     /* newlines are isspace() */
  57                 }
  58         }
  59
  60         // Ensure we're on a new line before printing.
  61         if (lastchar != '\n') {
  62                 putchar('\n');
  63         }
  64
  65         // Longest bar needs first print; find it.
  66         int longest_bar = 0;
  67         for (int bar = 1; bar <= MAX_CHARS; ++bar)
  68                 if (words[longest_bar] < words[bar])
  69                         longest_bar = bar;
  70
  71         /*
  72          * Print main graph.
  73          */
  74         for (int y = words[longest_bar]; y > 0; --y) {
  75                 // Y-axis
  76                 printf("%4d  | ", y);
  77
  78                 // Bars
  79                 for (int bar = 0; bar < MAX_CHARS; ++bar) {
  80                         if (words[bar] >= y)
  81                                 putchar(BAR_CHAR);
  82                         else
  83                                 putchar(' ');
  84                         printf(BAR_SEP);      /* bar separator */
  85                 }
  86                 putchar(BAR_CHAR);
  87                 putchar('\n');       /* avoid extra spaces */
  88         }
  89
  90         // Print bottom border.
  91         printf("      +-");
  92         for (int bar = 0; bar < MAX_CHARS; ++bar)
  93                 printf("---");
  94         printf("--\n");              /* avoid extra spaces */
  95
  96         // Print x-axis.
  97         printf("       ");
  98         for (int bar = 0; bar < MAX_CHARS; ++bar)
  99                 printf("%2d ", bar+1);
 100
 101         // Avoid extra spaces, and use '>' for last bar.
 102         printf(">%d\n", MAX_CHARS);
 103
 104         return EXIT_SUCCESS;
 105 }