C Primer Plus学习字符串和字符串函数（13）

采用选择排序算法排序指针来排序字符串：

#include 
#include 
#define SIZE 81   /*限制字符串长度，包括\0*/
#define LIM 20   /*可读入的最多行数*/
#define HALT ""    /*空字符串停止输入*/
void stsrt(char * strings[], int num);   /*字符串排序函数*/
char * s_gets(char * st, int n);
int main(void)
{
	char input[LIM][SIZE];  /*储存输入的数组*/
	char * ptstr[LIM];  /*内含指针变量的数组*/
	int ct = 0;   /*输入计数*/
	int k;  /*输出计数*/
	printf("Input up to %d lines, and I will sort them.\n", LIM);
	printf("To stop, press the Enter key at a line's start.\n");
	while (ct < LIM && s_gets(input[ct], SIZE) != NULL && input[ct][0] != '\0')
	{
		ptstr[ct] = input[ct];  /*设置指针指向字符串*/
		ct++;
	}
	stsrt(ptstr, ct);   /*字符串排序函数*/
	puts("\nHere's the sorted list:\n");
	for (k = 0; k < ct; k++)
	puts(ptstr[k]);   /*排序后的指针*/
	return 0;
}
void stsrt(char * strings[], int num)   /*字符串-指针-排序函数*/
{
	char * temp;
	int top, seek;
	for (top = 0; top < num - 1; top++)
	for (seek = top + 1; seek < num; seek++)
	if (strcmp(strings[top], strings[seek]) > 0)
	{
		temp = strings[top];
		strings[top] = strings[seek];
		strings[seek] = temp;
	}
}
char * s_gets(char * st, int n)
{
	char * ret_val;
	int i = 0;
	ret_val = fgets(st, n, stdin);
	if (ret_val)
	{
		while (st[i] != '\n' && st[i] != '\0')
		i++;
		if (st[i] == '\n')
		st[i] = '\0';
		else
		while (getchar() != '\n')
		continue;
	}
	return ret_val;
}

运行结果如下：