main.c

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

char* concatstr(char*,  char*);
int strlen(char*);
int strend(char*, char*);

//K&R的c语言指针章节练习题
int main(void)
{
	char *a = "hello1";
	char *b = "world2";
	char *c = concatstr(a, b);
	printf("%s\n", c);
	
	char *d = "hello";
	char *e = "llo";
	int result = strend(d, e);
	printf("%d", result);

	return(EXIT_SUCCESS);
}

//检查end字符数组是否位于main字符数组末端
int strend(char *main, char *end){
	char *result = main;
	char *last = end;
	int endlen = strlen(last);
	int index = 0, found = 0;
	while(*result){
		if(*result == *last){
			last++;
			if(++index == endlen){
				found = 1;
			}
		}
		else{
			index = 0;
			found = 0;
		}
		result++;
	}
	return found;
}

//连接指定字符数组, 并返回一个新的字符数组
char* concatstr(char *a,  char *b){
	char *c = malloc(strlen(a) + strlen(b) + 1);//new 'a new string'
	char *d = c;
	if(d){
		while(*a){
			*d = *a;
			d++;
			a++;
		}
		while(*d++ = *b++);
		*d = '\0';//
		return c;
	}
	return NULL;
}

//获取字符数组长度
int strlen(char *c){
	int len = 0;
	char *result = c;
	while(*result++){
		len++;
	}
	return len;
}