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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* The C Programming Language: 2nd Edition
*
* 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.
*/
#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 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);
}
}
}
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 */
if (argc > 1) {
int i, j;
for (i = 1, j = 0; --argc; i++) {
if (argv[i][j++] == '-') {
while (argv[i][j] != '\0') {
switch (argv[i][j]) {
case 'n':
numeric = 1;
break;
case 'r':
reverse = 1;
break;
}
j++;
}
}
}
}
if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
my_qsort((void **) lineptr, 0, nlines - 1, (int (*)(const char *, const char *))(numeric ? numcmp : strcmp));
if (reverse == 1) {
reverse_set(lineptr, nlines - 1);
}
writelines(lineptr, nlines);
return 0;
} else {
printf("Input too big to sort\n");
return 1;
}
}
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