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【问题】关于C++ string复制的问题？

2014/10/18镜像同步4 回复

这是编译原理留的作业，词法分析。我现在大概就是分析过后确定是个标识符，存到链表里面，然后输出。可是在调试的时候发现。运行到红色语句的时候，对tmpSign这个string进行修改，我链表中的first->id也进行修改，这是为什么呢？难道是指向同一内存？那么string该怎么复制？谢各位大神~~ 附代码： #include <iostream> #include <fstream> #include <string> using namespace std; struct sign{ string id; struct sign * next; }; struct sign * first= NULL, * last = NULL; int total = 0; bool isCharacter(char a); bool isDigit(char a); void add(string a); void handleWord(string a); void showSign(void); int main(int argc, char *argv[]) { cout << "Please input the name of the file." << endl; string name; cin >> name; ifstream source(name.c_str()); if (!source.is_open()){ cout << "Fail to open the file!"; exit(1); } string buffer; char temp; int count = 0; while (!source.eof()){ getline(source,buffer); count = 0; temp = buffer[count++]; while(temp != '\0'){//处理一个单词 if(isCharacter(temp)){ string tmpSign; int cur = 0; while((temp != ' ') && (temp != '\0')){//读取这个单词，循环的时候对tmpSign赋值，就发生错误了。。。 tmpSign[cur++] = temp; temp = buffer[count++]; } tmpSign[cur] = '\0'; handleWord(tmpSign); }else if(isDigit(temp)){ string num; int cur = 0; while(isDigit(temp)){ num[cur++] = temp; temp = buffer[count++]; } num[cur] = '\0'; add(num); }else{ //其他情况 } } } } showSign(); return 0; } bool isCharacter(char a){ if((a >= 65 && a <= 90)||(a >=97 && a <=122)) return true; else return false; } bool isDigit(char a){ if(a >= 48 && a <= 57) return true; else return false; } void handleWord(string a){ for(int i = 0; a[i] != '\0'; i++) if(!(isCharacter(a[i]) || a[i] == '_' || isDigit(a[i]))){ cout << "Illegal input!" << endl; return; } add(a); } void add(string a){ if(first == NULL){ first = new struct sign; first -> id = a; first -> next = NULL; last = first; }else{ struct sign * tempp = new struct sign; tempp -> id = a; tempp -> next = NULL; last -> next = tempp; last = tempp; } } void showSign(void){ struct sign * tep = first; cout << "Here are the signs." << endl; while(tep != NULL){ cout << tep -> id << endl; tep = tep -> next; } }

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