指针自写库函数（但肯定没有库函数高效）
解释都在注释里了，手机打字费劲
/** strlen1()用来测量一个字符串的有效长度* strcat1()将第二个字符串拼接到第一个字符串的后面* strcpy()将后一个字符串复制到前一个字符串* strcmp1()字符串比较函数，根据返回值判断哪个大小<1 == 2->0，1>2->1,1<2->-1>1.”A”<“B” 2.”A”<“AB” 3.”Apple”<“Banana”4.”A”<“a” 5.”compare”<“computer”* strlwr1()将字符串内大写字母全部转化为小写* strupr1()将字符串内小写字母全部转化为大写*/#include <stdio.h>int strlen1(char* pr);void strcat1(char* pr, char* qw);int strcmp1(char* pr, char* qw);void strlwr1(char* pr);void strupr1(char* pr);int main(void){char word1[100] = "LikeC";//足够位置保证可以让word2夫进来char word2[20] = "LikeJAVA";return 0;}int strlen1(char * pr)//pr保存word1首地址{int i = 0;while(* (pr+i) != '\0'){i++;}return i;}void strcat1(char * pr, char * qw)//传两个字符数组首地址{int i = 0,q = 0;while (*(pr + i) != '\0'){i++;}while (*(qw + q) != '\0'){*(pr + i) = *(qw + q);i++; q++;}}int strcmp1(char * pr, char * qw){int i = 0;while ((*(pr + i) == *(qw + i))&& (*(pr + i) != '\0')&& (*(qw + i) != '\0')){i++;}if (*(pr + i) > *(qw + i))return 1;if (*(pr + i) < *(qw + i))return -1;else return 0;}void strlwr1(char* pr){int i = 0;while (*(pr + i) != '\0'){if (*(pr + i) >= 'A' && *(pr + i) <= 'Z')*(pr + i) = *(pr + i)+32;i++;}}void strupr1(char* pr){int i = 0;while (*(pr + i) != '\0'){if (*(pr + i) >= 'a' && *(pr + i) <= 'z')*(pr + i) = *(pr + i) - 32;i++;}}
