实现strlen,strcpy,strcat,strstr

int Strlen(const char* str) int Strlen(const char* s){ int size=0; while(*str!='\0'){ size++; str++; } return size; } char* Strcpy(char* dest,const char* src) char* Strcpy(char* dest,const char* src){ if(dest==NULL||src==NULL){ return NULL; } char* result=dest; while(*src!='\0'){ *dest=*src; src++; dest++; } *dest='\0'; return result; }

-char* Strcat(char* dest,const char* src)

char* Strcat(char* dest,const char* src){ if(dest==NULL||src==NULL){ return NULL; } int cur=0; while(dest[cur]!='\0'){ cur++; } int i=0; while(src[i]!='\0'){ dest[cur+i]=src[i]; i++; } dest[cur+i]='\0'; return dest; } char* Strstr(const char* str1,const char* str2) char* Strstr(const char* str1,const char* str2){ const char* rp; const char* sp; if(str1==NULL||str2==NULL){ return NULL } while(*str1){ rp=str1; sp=str2; do{ if(!*sp) return str1; }while(*rp++==*sp++); str1++; } return NULL; }