C程序设计语言 （第二版） 练习 5-14
练习 5-14 修改排序程序，使它能处理-r标记。该标记表明，以逆序（递减）方式排序。要保证-r和-n能够组合在一起使用。
注意：代码在win32控制台运行，在不同的IDE环境下，有部分可能需要变更。
IDE工具：Visual Studio 2010
代码块：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>#define MAXLINES 5000
#define MAXLEN 1000
#define ALLOCSIZE 10000static char allocbuf[ALLOCSIZE];
static char *allocp = allocbuf;char *alloc(int n){if(allocbuf + ALLOCSIZE - allocp >= n){allocp += n;return allocp - n;}else{return 0;}
}void afree(char *p){if(p >= allocbuf && p < allocbuf + ALLOCSIZE){allocp = p;}
}char *lineptr[MAXLINES];int getline(char *s, int lim){int c;char *t = s;while(--lim > 0 && (c = getchar()) != EOF && c != '\n'){*s++= c;}if(c == '\n'){*s++ = c;}*s = '\0';return s - t;
}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';strcpy(p, line);lineptr[nlines++] = p;}}return nlines;
}void writelines(char *lineptr[], int nlines){while(nlines-- > 0){printf("%s\n", *lineptr++);}
}void swap(void *v[], int i, int j){void *temp;temp = v[i];v[i] = v[j];v[j] = temp;
}int numcmp(const void *s1, const void *s2){double v1, v2;v1 = atof(*(const char **)s1);v2 = atof(*(const char **)s2);if(v1 < v2){return -1;}else if(v1 > v2){return 1;}else{return 0;}
}void qsort(void *v[], int left, int right, int(*comp)(const void*, const void*), int sign){int i, last;if(left >= right){return;}swap(v, left, (left + right) / 2);last = left;for(i = left + 1; i <= right; i++){if(sign == 0){if((*comp)(v[i], v[left]) < 0){swap(v, ++last, i);}}if(sign == 1){if((*comp)(v[i], v[left]) > 0){swap(v, ++last, i);}}}swap(v, left, last);qsort(v, left, last - 1, comp, sign);qsort(v, last + 1, right, comp, sign);
}int main(int argc, char *argv[]){int nlines;int numeric = 0;int sign = 0;if(argc > 1){if(strcmp(argv[1], "-n") == 0){numeric = 1;sign = 0;}if(strcmp(argv[1], "-n") == 0 && strcmp(argv[2], "-r") == 0){numeric = 1;sign = 1;}}if((nlines = readlines(lineptr, MAXLINES)) >= 0){qsort((void**)lineptr, 0, nlines - 1, (numeric ? numcmp : (int (*)(const void *,const void *))strcmp), sign);writelines(lineptr, nlines);system("pause");return 0;}else{printf("Error: input too big to sort!\n");system("pause");return 1;}system("pause");return 0;
}
