C程序 对文本行进行排序

#include <stdio.h>
#include <string.h>
#include <stdlib.h> 

#define MAXLINES 5000     /* max #lines to be sorted */

char *lineptr[MAXLINES];  /* pointers to text lines */
int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);
void qsort(char *lineptr[], int left, int right);
/* sort input lines */
int main()
{
	int nlines;     /* number of input lines read */
    if ((nlines = readlines(lineptr, MAXLINES)) >= 0) {
	    qsort(lineptr, 0, nlines-1);
        writelines(lineptr, nlines);
		return 0;
    } else {
		printf("error: input too big to sort\n");
        return 1;
    }
}

#define MAXLEN 1000  /* max length of any input line */
int getline(char *, int);
char *alloc(int);
/* readlines:  read input lines */
int readlines(char *lineptr[], int maxlines)
{
	int len, nlines;
    char *p, line[MAXLEN];
    nlines = 0;
    while ((len = getline(line, MAXLEN)) > 0)
		if (nlines >= maxlines || (p = alloc(len)) == NULL)
			return -1;
		else {
			line[len-1] = '\0';  /* delete newline */
			strcpy(p, line);
			lineptr[nlines++] = p;
		}
	return nlines;
}

/* writelines:  write output lines */
void writelines(char *lineptr[], int nlines)
{
	int i;
	for (i = 0; i < nlines; i++)
	printf("%s\n", lineptr[i]);
}

/* qsort:  sort v[left]...v[right] into increasing order */
void qsort(char *v[], int left, int right)
   {
       int i, last;
       void swap(char *v[], int i, int j);
       if (left >= right)  /* do nothing if array contains */
           return;         /* fewer than two elements */
       swap(v, left, (left + right)/2);
       last = left;
       for (i = left+1; i <= right; i++)
           if (strcmp(v[i], v[left]) < 0)
               swap(v, ++last, i);
       swap(v, left, last);
       qsort(v, left, last-1);
       qsort(v, last+1, right);
   }

int getline(char s[],int lim)
   {
       int c, i;
       for (i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
           s[i] = c;
       if (c == '\n') {
           s[i] = c;
           ++i;
       }
       s[i] = '\0';
       return i;
   }

   /* swap:  interchange v[i] and v[j] */
   void swap(char *v[], int i, int j)
   {
       char *temp;
	   temp = v[i];
       v[i] = v[j];
       v[j] = temp;
   }


   #define ALLOCSIZE 10000 /* size of available space */
   static char allocbuf[ALLOCSIZE]; /* storage for alloc */
   static char *allocp = allocbuf;  /* next free position */
   char *alloc(int n)    /* return pointer to n characters */
   {
       if (allocbuf + ALLOCSIZE - allocp >= n) {  /* it fits */
           allocp += n;
		              return allocp - n; /* old p */
       } else      /* not enough room */
           return 0;
   }

   

 

评论

1 楼 newlangwen1 2011-08-23  

你好 我想请教个问题，我运行了一下上面的程序，结果是输入什么就输出什么，未进行排序，为什么呢？