添加更多数据后，C++ Vector 迭代器不可取消引用

Question

同志们，

以下不起作用:

vector<string>::iterator c;

for( c = holdtype.begin(); c != holdtype.end(); c++)
{ 
    if( *c == "preposition" )
    {
        c++; 
        if( *c == "unknown" )
        {       
            c++;  
            if( *c == "unknown" )
            {
                c++;  
                if( *c == "unknown" )
                {
                    cout <<endl <<"This should be a verb " << *c;
                }
            }
        }
    } 
}

奇怪的是它适用于一定数量的数据。一旦超过大约 30 个字，它就会停止工作并给我“不可取消引用的错误”。

我已经试过了，结果是一样的:

vector<string>::iterator c;
c = holdtype.begin();

while( c != holdtype.end())
{ 
    if( *c == "preposition" )
    {
        if( c != holdtype.end() ) { c++; } else { break; }
        if( *c == "unknown" )
        {       
            if( c != holdtype.end() ) { c++; } else { break; }
            if( *c == "unknown" )
            {
                if( c != holdtype.end() ) { c++; } else { break; }
                if( *c == "unknown" )
                {
                    cout <<endl <<"This should be a verb " << *c;
                }
            }
        }
    } 
    if( c == holdtype.end() ) { break; } else {c++;}
}

几天来我一直在努力解决这个问题，我是初学者。

Answer 1

您的第二个版本几乎是正确的，但是您需要在递增之后和取消引用之前检查 c 是否有效:

vector<string>::iterator c;
c = holdtype.begin();

while( c != holdtype.end())
{ 
    if( *c == "preposition" )
    {
        ++c;
        if( c == holdtype.end() ) { break; }
        if( *c == "unknown" )
        {       
            ++c;
            if( c == holdtype.end() ) { break; }
            if( *c == "unknown" )
            {
                ++c;
                if( c == holdtype.end() ) { break; }
                if( *c == "unknown" )
                {
                    cout <<endl <<"This should be a verb " << *c;
                }
            }
        }
    } 
    ++c;
}