二叉树最近公共父节点

#include <bits/stdc++.h>
using namespace std;
struct TreeNode
{
int val;
TreeNode*left;
TreeNode*right;
TreeNode(int x):
val(x),left(NULL),right(NULL) {}
};
int k;
int x,y;
void create(TreeNode*root,int n)
{
if(n==1)return;
root->left=new TreeNode(root->val-pow(2,n-2));
root->right=new TreeNode(root->val+pow(2,n-2));
create(root->left,n-1);
create(root->right,n-1);
}
//针对二叉排序树
TreeNode*findTreeNode(TreeNode*root,int n)
{
if(root->val==n)return root;
else if(root->val<n)return findTreeNode(root->right,n);
else findTreeNode(root->left,n);
}
//方法一：针对所有二叉树结构，复杂度较高
TreeNode*findCommonParent(TreeNode*root,TreeNode*p,TreeNode*q)
{
if(root==NULL||p==root||q==root)return root;
TreeNode*leftNode=findCommonParent(root->left,p,q);
TreeNode*rightNode=findCommonParent(root->right,p,q);
if(leftNode&&rightNode)return root;
else if(leftNode)return leftNode;
else return rightNode;
}
//方法二：针对二叉树平排序结构，复杂度较低
TreeNode*findCommonParent1(TreeNode*root,TreeNode*p,TreeNode*q)
{
int min,max;
if(p->val<q->val)min=p->val,max=q->val;
else min=q->val,max=p->val;
while(root)
{
if(root->val>=min&&root->val<=max)return root;
else if(root->val<min&&root->val<max)root=root->right;
else root=root->left;
}
return NULL;
}
//获得根节点到某一节点路径
bool getNodePath(TreeNode*root,TreeNode*p,list<TreeNode*>&l)
{
if(root==NULL||p==NULL)return false;
l.push_back(root);
if(root==p)return true;
bool found=false;
if(root->left)found=getNodePath(root->left,p,l);
if(!found&&root->right)found=getNodePath(root->right,p,l);
if(!found)l.pop_back();
return found;
}
//方法三：针对所有二叉树结构，复杂度较低
TreeNode*findCommonParent2(TreeNode*root,TreeNode*p,TreeNode*q)
{
list<TreeNode*>l1,l2;
getNodePath(root,p,l1);
getNodePath(root,q,l2);
reverse(l1.begin(),l1.end());
reverse(l2.begin(),l2.end());
list<TreeNode*>::iterator it1=l1.begin(),it2=l2.begin();
if(l1.size()>l2.size())
{
for(int i=0; i<l1.size()-l2.size(); i++)
it1++;
}
else
{
for(int i=0; i<l2.size()-l1.size(); i++)
it2++;
}
for(; it1!=l1.end()&&it2!=l2.end(); it1++,it2++)
{
if(*it1==*it2)
{
return *it1;
break;
}
}
return NULL;
}
//前序遍历
void print(TreeNode*root)
{
if(root==NULL)return;
cout<<root->val<<endl;
print(root->left);
print(root-&g
4000
t;right);
}
int main()
{
while(cin>>k>>x>>y)
{
TreeNode*root=new TreeNode(pow(2,k-1));
create(root,k);
TreeNode*p=findTreeNode(root,x);
TreeNode*q=findTreeNode(root,y);
TreeNode*commonParent=findCommonParent(root,p,q);
cout<<"方法一："<<commonParent->val<<endl;
TreeNode*commonParent1=findCommonParent1(root,p,q);
cout<<"方法二："<<commonParent1->val<<endl;
TreeNode*commonParent2=findCommonParent2(root,p,q);
cout<<"方法三："<<commonParent2->val<<endl;
}
return 0;
}