我正在为电影租赁业务制作二元搜索树(理论上)。如果键入了电影租赁业务所没有的标题,我需要输出“未找到电影”。我不知道如何在没有每次都出现分段错误的情况下执行此操作。我不知道还有什么可以尝试我这个代码是有道理的。我只是一个初学者 - 请放轻松我。任何帮助将不胜感激! (你可以找到我的if函数试图在我的代码末尾的三个斜杠(///)之间输出“未找到电影”。
void MovieTree::rentMovie(std::string title)
{
MovieNode *foundMovie = root;
//MovieNode *parent = NULL;
if (root == NULL)
{
cout << "Movie not found." << endl;
return;
}
else
{
foundMovie = root;
while (foundMovie != NULL)
{
if (foundMovie == NULL) //tree is empty
{
cout << "Movie not found." << endl;
}
else
{
if (foundMovie->title.compare(title) > 0) //uses ASCII to determine where titles are
{
foundMovie->parent = foundMovie;
foundMovie = foundMovie ->leftChild;
//cout << "printed left" << endl; //debugging
if (foundMovie->title.compare(title) == 0 && foundMovie->quantity > 0)
{
foundMovie->quantity--;
cout << "Movie has been rented." << endl;
//Title entered matches title found
cout << "Movie Info:" << endl;
cout << "===========" << endl;
cout << "Ranking:" << foundMovie->ranking << endl;
cout << "Title:" << foundMovie->title << endl;
cout << "Year:" << foundMovie->year << endl;
cout << "Quantity:" << foundMovie->quantity << endl;
break;
}
else if (foundMovie->quantity ==0)
{
//If movie is out of stock
cout << "Movie out of stock." << endl;
break;
}
}
else //check rightChild
{
foundMovie->parent = foundMovie;
foundMovie = foundMovie->rightChild;
//cout << "printed right" << endl; //debugging
if (foundMovie->title.compare(title) == 0 && foundMovie->quantity > 0) //title entered matches title found
{
foundMovie->quantity--;
cout << "Movie has been rented." << endl;
cout << "Movie Info:" << endl;
cout << "===========" << endl;
cout << "Ranking:" << foundMovie->ranking << endl;
cout << "Title:" << foundMovie->title << endl;
cout << "Year:" << foundMovie->year << endl;
cout << "Quantity:" << foundMovie->quantity << endl;
break;
}
else if (foundMovie->quantity ==0)
{
//movie is found but out of stock
cout << "Movie out of stock." << endl;
break;
}
}
}
}
///
if (foundMovie->title == title)
{
cout << "found the movie" << endl;
}
else
{
cout << "Movie not found." << endl;
}
///
}
}
答案 0 :(得分:1)
代码中的一些评论/错误
您可以删除不再有用的条件:它会降低代码的可读性。
while (foundMovie != NULL)
{
if (foundMovie == NULL) // false by construction!!!
...
}
foundMovie->parent = foundMovie;
应该会消失。它创建了一个循环依赖!
您的上一个语句if (foundMovie->title == title)
可能会导致分段错误
此时foundMovie
可以为NULL。
这是一个可能的重写:
void MovieTree::rentMovie(std::string title)
{
MovieNode *foundMovie = root;
if (root == NULL)
{
cout << "Movie not found." << endl;
return;
}
foundMovie = root;
while (foundMovie != NULL)
{
int compareTitle = foundMovie->title.compare(title); //uses ASCII to determine where titles are
if (compareTitle > 0)
{
foundMovie = foundMovie ->leftChild;
}
else if (compareTitle < 0) //check rightChild
{
foundMovie = foundMovie->rightChild;
}
else { // compareTitle == 0
if (foundMovie->quantity > 0)
{
foundMovie->quantity--;
cout << "Movie has been rented." << endl;
//Title entered matches title found
cout << "Movie Info:" << endl;
cout << "===========" << endl;
cout << "Ranking:" << foundMovie->ranking << endl;
cout << "Title:" << foundMovie->title << endl;
cout << "Year:" << foundMovie->year << endl;
cout << "Quantity:" << foundMovie->quantity << endl;
break;
}
else if (foundMovie->quantity ==0)
{
//If movie is out of stock
cout << "Movie out of stock." << endl;
break;
}
}
}
// be sure that foundMovie->title == title is equivalent to foundMovie->title.compare(title) == 0
if (foundMovie && foundMovie->title == title)
{
cout << "found the movie" << endl;
}
else
{
cout << "Movie not found." << endl;
}
}