线性时间排序(三)C语言

  给定若干字符串,也就是二维数组,字符串指针之类的.如 ab, a, b.要求排序后为 a, ab, b.字母数为 N ,在 O(N)时间完成.这个问题,是昨天那个问题的下一个问题.我起初的方向是错的.后来,采用了分治的方法给予实现.关于时间的分析, 每次都只对当前位置不为 NUL 的字符进行排序.所以,当然就是 O(N)了.确实,是这样.字母的范围,也是可以通过宏来更改的,非常方便.有实用价值.

  写博客是个好习惯,能够梳理我的思绪,同样也是写代码时的期待.

  字符串,是一个我一直回避的问题.昨天和今天,接触了不少,各种操作什么的.

  今天做了09上的题,上午下午都通过了.呵呵.我整天干着如此健脑的事情.

  这个东西,知识点比较多.都是基数排序的思想,运用到具体问题.我想,对于这一块,我能够解决一部分问题.

  脑袋比较昏沉,再睾一会去睡觉.

  当然,这个东西也给我带来了很多问题.编译方面的,宏重定义莫名地出现,如何一次性为一个函数分配存储空间,而不用频繁分配.都是待解决的问题.

  好吧,贴出我的代码.

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/*8-3-b-2011-04-28-23.39.c -- 第八章第三题b*/#include <stdio.h>#include <stdlib.h>#include <string.h>#define NUL ('/0')#define MIN ('a')#define MAX ('z')#define RANGE (MAX - MIN + 2)/*From NUL to 'z'.*/#define LENTH (20)#define SIZE (20)int main (void) ;void sort (char array[][LENTH], const int start, const int end, const int index) ;int countingSort (char array[][LENTH], const int start, const int end, const int index) ;void swap (char * pSL, char * pSR) ;void printResult (char array[][LENTH], const int size) ;int main (void){char array[SIZE][LENTH] = {"abbb", "abbc", "abbd", "bbab", "ccac", "ccaca", "ccbc", "cca", "oiu", "z", "oiu", "qqa", "kiss", "uyuy", "iuiu", "b", "c", "faff", "fafe", "fab",} ;int size = SIZE ;sort (array, 0, size - 1, 0) ;printResult (array, size) ;return 0 ;}void sort (char array[][LENTH], const int start, const int end, const int index){int i, j ;/*Sort array as index from start to end.*/if (0 == countingSort (array, start, end, index)){puts ("Out of space.") ;return ;}for (i = start; i <= end; i = j){while (NUL == array[i][index])i++ ;for (j = i + 1; j <= end; j++){if (array[j][index] != array[j - 1][index])break ;}/*Will not call sort when i == j - 1.*/if (i != j - 1)sort (array, i, j - 1, index + 1) ;}}int countingSort (char array[][LENTH], const int start, const int end, const int index){char * * sorted ;int * count ;int lenth, i, j ;count = (int *) malloc (sizeof (int) * RANGE) ;if (NULL == count)return 0 ;lenth = end - start + 1 ;sorted = (char * *) malloc (sizeof (char *) * lenth) ;if (NULL == sorted){free (count) ;return 0 ;}for (i = 0; i < lenth; i++){sorted[i] = (char *) malloc (sizeof (char) * LENTH) ;if (NULL == sorted[i]){for (j = i - 1; j >= 0; j--)free (sorted[j]) ;free (sorted) ;free (count) ;return 0 ;}}for (i = 0; i < RANGE; i++)count[i] = 0 ;for (i = start; i <= end; i++){if (array[i][index] != NUL)count[array[i][index] - 'a' + 1]++ ;elsecount[0]++ ;}for (i = 1; i < RANGE; i++)count[i] += count[i - 1] ;for (i = end; i >= start; i--){if (array[i][index] != NUL)strcpy (sorted[--count[array[i][index] - 'a' + 1]], array[i]) ;elsestrcpy (sorted[--count[0]], array[i]) ;}for (i = start, j = 0; i <= end; i++, j++)strcpy (array[i], sorted[j]) ;free (count) ;for (i = 0; i < lenth; i++)free (sorted[i]) ;free (sorted) ;return 1 ;}void swap (char * pSL, char * pSR){char temp[LENTH] ;strcpy (temp, pSL) ;strcpy (pSL, pSR) ;strcpy (pSR, temp) ;}void printResult (char array[][LENTH], const int size){int i ;for (i = 0; i < size; i++)printf ("%s/n", array[i]) ;}