库函数strcpy,strcat,strcmp,shrlen的实现

char* mystrcpy(char* str, const char* ptr){char* ret = str;assert(str);assert(ptr);while ((*str++= *ptr++) && ptr != '\0'){;}return ret;}char* mystrcat(char* str, const char* ptr){char* ret = str;assert(str);assert(ptr);while (*str)str++;while ((*str++= ptr++) != '\0'){;}return ret;}int mystrcmp(const char* str1, const char* str2){int ret = 0;assert(str1);assert(str2);while (!(ret =str2 -str1)&& *str1){str1++;str2++;}if (ret < 0)ret = -1;else if (ret>0)ret = 1;return ret;}int mystrlen(const char* str){assert(str);int len = 0;if (*str++ != '\0')len++;}