String类的增删查改

class String{public:friend ostream& operator<<(ostream& os,const String&s){os<<s._size<<" "<<s._capatity<<" "<<s._str<<endl;return os;}String(const char*str=""):_size(strlen(str)),_capatity(_size),_str(new char[strlen(str)+1]){strcpy(_str,str);}String(const String& s):_size(strlen(s._str)),_capatity(s._size),_str(new char[strlen(s._str)+1]){strcpy(_str,s._str);}String& operator=(const String&s){if(this!=&s){char* tmp=new char[strlen(s._str)+1];    delete[]_str;    strcpy(tmp,s._str);    _str=tmp;   _size=strlen(_str);   _capatity=strlen(_str);}return *this;}~String(){if(_str!=NULL){delete[]_str;_str=NULL;}}char& operator[](size_t pos){return _str[pos];}bool operator==(const String&s)const{int i=0;for(i=0;i<_size&&i<s._size;i++){if(_str[i]!=s._str[i]){return false;}}if(i==_size&&i==s._size)return true;elsereturn false;}bool operator<(const String&s)const{int i=0;for(i=0;i<_size&&i<s._size;i++){if(_str[i]<s._str[i])return true;if(_str[i]>s._str[i])return false;}if(i==_size&&i!=s._size)return true;elsereturn false;}bool operator !=(const String&s)const{return !(*this==s);}bool operator>(const String&s)const{return !(*this<s);}bool operator<=(const String&s)const{return (*this<s)||(*this==s);}bool operator>=(const String&s)const{return (*this>s)||(*this==s);}void Expand(size_t n){if(n>_capatity){_str=(char*)realloc(_str,n+1);assert(_str);_capatity=n;}}void Pushback(char ch){if(_size=_capatity){Expand(_capatity*2);}_str[_size++]=ch;_str[_size]='\0';}void Pushback( char* str){size_t len=strlen(str);if(_size+len>_capatity){Expand(_size+len);}strcpy(_str+_size,str);_size+=len;}void Popback(){assert(_str);_str[--_size]='\0';}void Insert(size_t pos,char ch){assert(_str);size_t end=_size;while(pos<=end){_str[end+1]=_str[end];--end;}_str[pos]=ch;_size++;}void Insert(size_t pos,char* str){   assert(_str);size_t len=strlen(str);if(_size+len>_capatity){Expand(_size+len);}int end=_size;while(pos<=end){_str[end+len]=_str[end];--end;}while(*str){_str[pos++]=*str++;}_size+=len;}void Erase(size_t pos,size_t len){assert(_str); if(pos+len>_size){_str[pos]='\0';_size=pos;}else{strcpy(_str+pos,_str+pos+len);_size-=len;}}    int Find(char ch){int i=0;int pos=0;size_t len=strlen(_str);for(i=0;i<len;i++){if(_str[i]==ch)return pos;pos++;}/*while(*_str++){if(*_str==ch){return pos;}pos++;}*/return -1;}