《C程序设计语言》练习3-3

题目：编写函数expand(s1, s2)，将字符串s1中类似于a-z一类的速记符号在字符串s2中扩展为等价的完整列表abc...xyz。该函数可以处理大小写字母和数字，并可以处理a-b-c、a-z0-9与-a-z等类似的情况。作为前导和尾随的-字符原样打印。

自己的代码：

/* 	编写函数expand(s1, s2)，将字符串s1中类似于a-z一类
	的速记符号在字符串s2中扩展为等价的完整列表abc...xyz。
	该函数可以处理大小写字母和数字，并可以处理a-b-c、
	a-z0-9与-a-z等类似的情况。作为前导和尾随的-字符原样打印。 
 */
 
 #include 
 #include 
 #include 
 #define N 100
 
 enum {ALPHA, NUMBER, OTHER} type; /* 字符类型 */ 

 void expand(char *s1, char *s2)
 {
 	int in = 0;
 	int i, j, k = 0;
 	int end;
 	char tmp;
 	
 	for(i = 0, k = 0; s1[i] != '\0'; i++){
 		if(isalpha(s1[i]))
 			type = ALPHA;
		else if(isdigit(s1[i]))
			type = NUMBER;
		else
			type = OTHER;
			
 		if(!in && (type == OTHER)){
		 	s2[k++] = s1[i];
		 	continue;
	 	}
	 	if(type == ALPHA && !in){
		 	in = 1;
		 	for(tmp = s1[i], end = i + 1; (isalpha(s1[end]) && s1[end] > tmp) || s1[end] == '-'; end++)
		 		if(isalpha(s1[end]))
			 		tmp = s1[end];
	 		end--;
	 		while(!isalpha(s1[end]))
	 			end--;
 			for(tmp = s1[i]; tmp <= s1[end]; tmp++){
				s2[k++] = tmp; 
		 	}
		 	i = end;
		 	in = 0;
		 	continue;
	 	}
	 	if(type == NUMBER && !in){
		 	in = 1;
		 	for(tmp = s1[i], end = i + 1; (isdigit(s1[end]) && s1[end] > tmp) || s1[end] == '-'; end++)
		 		if(isdigit(s1[end]))
			 		tmp = s1[end];
	 		end--;
	 		while(!isdigit(s1[end]))
	 			end--;
 			for(tmp = s1[i]; tmp <= s1[end]; tmp++){
				s2[k++] = tmp; 
		 	}
		 	i = end;
		 	in = 0;
		 	continue;
	 	}
 	}
 	s2[k] = '\0';
}

 /* 测试 */
 int main()
 {
 	char s1[N], s2[N];
 	
 	while(scanf("%s", s1) != EOF){
 		expand(s1, s2);
 		printf("%s\n", s2);
 	}
 	return 0;
 }

参考答案：

/* expand: expand shorthand notation in s1 into string s2 */
void expand(char s1[], char s2[])
{
	char c;
	int i, j;
	i = j = 0;
	while((c = s1[i++]) != '\0')	/* fetch a char from s1[] */
		if(s1[i] == '-' && s1[i+1] >= c) {
			i++;
			while(c < s1[i])	/* expand shorthand */
				s2[j++] = c++;
		} else	
			s2[j++] = c;	/* copy the character */
	s2[j] = '\0';
}

参考答案由德国Osnabruck大学的Axel Schreiner提供。

大师的代码比我的简短多了，膜拜~