diff options
Diffstat (limited to 'ch5')
| -rw-r--r-- | ch5/5-14_rsort.c | 2 | ||||
| -rw-r--r-- | ch5/5-15_sort-fold.c | 178 |
2 files changed, 179 insertions, 1 deletions
diff --git a/ch5/5-14_rsort.c b/ch5/5-14_rsort.c index 4928f80..4c03191 100644 --- a/ch5/5-14_rsort.c +++ b/ch5/5-14_rsort.c @@ -4,7 +4,7 @@ /* The C Programming Language: 2nd Edition * - * Exercise 5-13: Modify the sort program to handle a -r flag, which + * Exercise 5-14: Modify the sort program to handle a -r flag, which * indicates sorting in reverse (decreasing) order. Be sure that -r works * with -n. */ diff --git a/ch5/5-15_sort-fold.c b/ch5/5-15_sort-fold.c new file mode 100644 index 0000000..1eccc34 --- /dev/null +++ b/ch5/5-15_sort-fold.c @@ -0,0 +1,178 @@ +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> + +/* The C Programming Language: 2nd Edition + * + * Exercise 5-15: Add the option -f to fold upper and lower case together, so + * that case distinctions are not made during sorting; for example, a and A + * compare equal. + */ + +#define MAXLINES 5000 +char *lineptr[MAXLINES]; + +#define MAXLEN 1000 +#define DEFAULT_LINES 10 +#define ALLOCSIZE 10000000 + +static char allocbuf[ALLOCSIZE]; +static char *allocp = allocbuf; +char *alloc(int); + +int readlines(char *lineptr[], int nlines); +void writelines(char *lineptr[], int nlines); +void reverse_set(char *lineptr[], int nlines); +void my_qsort(void *lineptr[], int left, int right, int (*comp)(const char *, const char *)); +int numcmp(const char *, const char *); +void line_tolower(char *s); +int istrcmp(const char *, const char *); + +void my_qsort(void *v[], int left, int right, int (*comp)(const char *, const char *)) { + int i, last; + void swap(void *v[], int, int); + + if (left >= right) { + return; + } + swap(v, left, (left + right) / 2); + last = left; + for (i = left + 1; i <= right; i++) { + if ((*comp)(v[i], v[left]) <= 0) { + swap(v, ++last, i); + } + } + swap(v, left, last); + my_qsort(v, left, last - 1, comp); + my_qsort(v, last + 1, right, comp); +} + +int numcmp(const char *s1, const char *s2) { + double v1, v2; + + v1 = atof(s1); + v2 = atof(s2); + if (v1 < v2) { + return -1; + } else if (v1 > v2) { + return 1; + } else { + return 0; + } +} + +void swap(void *v[], int i, int j) { + void *temp; + + temp = v[i]; + v[i] = v[j]; + v[j] = temp; +} + +int readlines(char *lineptr[], int maxlines) { + int len, nlines; + char *p, line[MAXLEN]; + nlines = 0; + while ((len = mygetline(line, MAXLEN)) > 0) { + if (nlines >= maxlines || (p = alloc(len)) == NULL) { + return -1; + } else { + line[len-1] = '\0'; + strcpy(p, line); + lineptr[nlines++] = p; + } + } + return nlines; +} + +void writelines(char *lineptr[], int nlines) { + int i = 0; + for (; i < nlines && lineptr[i] != NULL; i++) { + printf("%s\n", lineptr[i]); + } +} + +void reverse_set(char *lineptr[], int nlines) { + int i; + int j = nlines; + for (i = 0; i < (nlines / 2); i++, j--) { + if (i < nlines) { + swap((void **)lineptr, i, j); + } + } +} + +/* Lowercase the entire line */ +void line_tolower(char *s) { + int i; + for (i = 0; s[i] != '\0'; i++) { + s[i] = tolower(s[i]); + } +} + +/* Ignore character case, then send results to qsort */ +int istrcmp(const char *s1, const char *s2) { + for ( ; tolower(*s1) == tolower(*s2); s1++, s2++) { + if (*s1 == '\0') { + return 0; + } + } + return tolower(*s1) - tolower(*s2); +} + +int mygetline(char *line, int lim) { + int c, i; + for (i = 0; i < lim && (c = getchar()) != EOF && c != '\n'; i++) { + *(line++) = c; + } + if (c == '\n') { + i++; /* I count newlines; some don't */ + *(line++) = c; + } + *line = '\0'; + return i; +} + +char *alloc(int n) { + if (allocbuf + ALLOCSIZE - allocp >= n) { + allocp += n; + return allocp - n; + } else { + return 0; + } +} + +/* sort input lines */ +int main (int argc, char *argv[]) { + int nlines; /* number of input lines read */ + int numeric = 0; /* 1 if numeric sort */ + int reverse = 0; /* 1 if reverse sort */ + int fold = 0; /* 1 if folding upper and lower case */ + + if (argc > 1) { + int i; + for (i = 1; --argc; i++) { + if (strcmp(argv[i], "-n") == 0) { + numeric = 1; + } else if (strcmp(argv[i], "-r") == 0) { + reverse = 1; + } else if (strcmp(argv[i], "-f") == 0) { + fold = 1; + } + } + } + if ((nlines = readlines(lineptr, MAXLINES)) >= 0) { + /* The trick is to chain inline if-statements. This will point to the correct + function for comparison, which powers my_qsort */ + my_qsort((void **) lineptr, 0, nlines - 1, (int (*)(const char *, const char *))(numeric ? numcmp : (fold ? istrcmp : strcmp))); + if (reverse == 1) { + reverse_set(lineptr, nlines - 1); + } + writelines(lineptr, nlines); + return 0; + } else { + printf("Input too big to sort\n"); + return 1; + } +} |