[英]how to return the pointer of a specific value in a tree in C?
using this struct:使用这个结构:
typedef struct node {
int content;
struct node* right;
struct node* left;
}Node;
I'm trying to write a code that return the pointer of the the node if node ->content== x I have tried this so far but I don't think its right:我正在尝试编写一个代码来返回节点的指针 if node ->content== x 我到目前为止已经尝试过了,但我认为它不正确:
Node* find (Node* p,int x)
{
Node* L,*R;
if(p==NULL)
retutn NULL;
L=find(p->left,x);
if(L->content == x)
return L;
R=find(p->right,x);
if(R->content == x)
return R;
}
can u help me correct my code?你能帮我纠正我的代码吗?
First, the code doesn't even compile because of retutn
.首先,由于
retutn
,代码甚至无法编译。
L=(p->left,x); // Equivalent to: L = x;
should be应该
L=find(p->left,x);
Same idea for the right side.右侧的想法相同。
L
could be NULL. L
可以是 NULL。
if(L->content == x)
should be应该
if(L != NULL)
or just要不就
if(L)
Same idea for the right side.右侧的想法相同。
You never check if the current node is a match.您永远不会检查当前节点是否匹配。 You need to add the following:
您需要添加以下内容:
if ( p->content == x )
return p;
The following is correct:以下是正确的:
Node* L, *R;
However, it's very easy to accidentally do但是,很容易不小心做
Node* L, R;
Maybe you should avoid grouping such declarations.也许您应该避免对此类声明进行分组。 On the plus side, this should be caught at compile-time (unless you avoid turning on even the most basic warnings).
从好的方面来说,这应该在编译时被捕获(除非你避免打开最基本的警告)。
All together,全部一起,
Node* find(Node* p, int x)
{
if ( !p )
return NULL;
if ( p->content == x )
return p;
Node* L = find( p->left, x );
if ( L )
return L;
Node* R = find( p->right, x );
if ( R )
return R;
return NULL;
}
The part of the function starting from these statements从这些语句开始的 function 部分
L=find(p->left,x);
if(L->content == x)
return L;
is incorrect.是不正确的。 For starters it is unclear why the node pointed to by the pointer p is not checked.
对于初学者来说,不清楚为什么不检查指针 p 指向的节点。 And the call of the function can return a null pointer.
而function的调用可以返回一个null指针。 So this if statement can invoke undefined behavior.
所以这个 if 语句可以调用未定义的行为。
The function definition depends on whether it is a binary search tree or not. function 定义取决于它是否是二叉搜索树。 That is whether nodes of the tree are ordered.
那就是树的节点是否有序。
If it is not a binary search tree then the function can be defined the following way如果它不是二叉搜索树,则可以通过以下方式定义 function
Node * find( const Node *root, int x )
{
if ( root == NULL )
{
return NULL;
}
else if ( root->content == x )
{
return ( Node * )root;
}
else
{
Node *p = find( root->left, x );
p == NULL ? return find( root->right, x ) : p;
}
}
If the tree is a binary search tree then the function can look the following way如果树是二叉搜索树,那么 function 可以如下所示
Node * find( const Node *root, int x )
{
if ( root == NULL )
{
return NULL;
}
else if ( x < root->content )
{
return find( root->left, x );
}
else if ( root->content < x )
{
return find( root->right, x );
}
else
{
return ( Node * )root;
}
}
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