编译器错误。预期的 ';'令牌前

Question

//this application implements use of a simple set
//program does data insertion,searching, and deletion
//program will represent a set of keys
//a user can add a key, delete a key, and check for duplicate keys
#include<iostream>
#include<set>
#include<string>
using namespace std;

int main()
{
string key, answer,answer2;
int i;

std::set<std::string> Keyring;

//prompts user to insert elements in set
for(i = 0; i < 5; i++)
{
cout<<"\nInsert Key " <<i+1<<" Onto Key Ring. Use _ For Spaces"<<endl;
cin >>key;
Keyring.insert(key);

}
//shows resulting key ring
cout<<"\nHere is Completed Key Ring\n"<<endl;
for(std::set<std::string>::iterator it=Keyring.begin(); it !=Keyring.end(); it++) //the '<' operator keeps UNIQUE elements in sorted order
{
std::cout<<" "<<"\n"<< *it; 
}


//Set Deletion and Addition
cout<<"\nWould You Like to Add or Delete From Key Ring?"<<endl;
cout<<"\nType add or delete"<<endl;
cin>>answer;

if(answer=="add")
{
cout<<"\nAdd Another Key. Use _ For Spaces"<<endl;
cin>>key;
Keyring.insert(key);

    if(Keyring.insert(key).second) //checks to see if key already present in set
    {
    cout<<key<<" Successful Addition!"<<endl;
    }   
    else if(!Keyring.insert(key).second)
    {
    cout<<" Duplicate Key Can't Be Added!"<<endl;
    }
}
else(answer=="delete")
{
cout<<"\nDelete A Key. Use _ For Spaces"<<endl;
cin>>key;
Keyring.erase(key);
cout<<"\nNew Keyring"<<endl;
}

for(std::set<std::string>::iterator it=Keyring.begin(); it !=Keyring.end(); it++)
{
std::cout<<" "<<"\n"<< *it;
}
cout<<"\nKeyring size is "<<Keyring.size()<<endl;

//Set Searching
cout<<"\nWant To Search For A Key y/n?"<<endl;
cin>>answer2;

if(answer2=="y")
{
cout<<"\nSearch For A Key. Use _ For Spaces"<<endl;
cout<<"\nWhere Is My..."<<endl;
cin>>key; cout<<" Key?"<<endl;
}
std::set<std::string>::iterator it=Keyring.find(key);

if(it !=Keyring.end())
{
cout<<key<<"\nFound!"<<endl;
}
else
{
cout<<key<<"\nNot Found :("<<endl;
}

return 0;

}

我不能运行我的程序，因为这个错误：[错误] expected ';'在“{”标记之前。问题从 'Set Addition and Deletion' 部分开始。问题在于该部分中的大 If-Else 语句，位于 else 语句开始的行。我已经看了一个小时了，这太令人沮丧了！编译器说应该有一个';'在 'else' 语句行之前，但在语法方面一切看起来都很好。我检查了嵌套 if 语句的文档，这样我就可以避免这个问题。需要帮助！

Answer 1

else(answer=="delete")应该是else if(answer=="delete")，C++没有任何特殊的elif形式所以你需要在else之后开始一个新的if块如果你想检查另一个条件。

像("delete" == answer)一样在比较运算符的左边写字面量也是个好主意，这样你可以很容易地检测到意外的赋值错别字。

编译器错误。预期的 ';'令牌前

Compiler Error. Expected ';' Before Token

c++

syntax

conditional

if-statement