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🌎个人专栏:《Linux操作系统》《经典算法试题 》《C++》 《数据结构与算法》

☀️走在路上，不忘来时的初心

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一、二叉搜索树与双向链表

1、题目讲解

2、思路讲解+递归展开图

3、代码实现

class Solution {
public:void _Convert(TreeNode* cur,TreeNode*& prev){if(cur==nullptr)return;_Convert(cur->left,prev);cur->left=prev;if(prev){prev->right=cur;}prev=cur;_Convert(cur->right,prev);}TreeNode* Convert(TreeNode* pRootOfTree) {TreeNode* cur=pRootOfTree,*prev=nullptr;_Convert(cur,prev);TreeNode* root=pRootOfTree;while(root && root->left){root=root->left;}return root;   }
};

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二、从前序遍历和中序遍历中构建二叉树

1、题目讲解

2、思路讲解+递归展开图

3、代码实现

class Solution {
public:TreeNode* _buildTree(vector<int>& preorder, vector<int>& inorder,int& i,int begin,int end){if(begin>end)return nullptr;int rooti=begin;while(rooti<=end){if(preorder[i]==inorder[rooti])break;rooti++;}TreeNode* root=new TreeNode(preorder[i++]);root->left=_buildTree(preorder,inorder,i,begin,rooti-1);root->right=_buildTree(preorder,inorder,i,rooti+1,end);return root;}TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {int i=0;TreeNode* root=_buildTree(preorder,inorder,i,0,inorder.size()-1);return root;}
};

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三、从中序遍历和后序遍历中构建二叉树

1、题目讲解

2、思路讲解

3、代码实现

class Solution {
public:TreeNode* _buildTree(vector<int>& inorder, vector<int>& postorder,int& i,int begin,int end){if(begin>end)return nullptr;int rooti=begin;while(begin<=end){if(postorder[i]==inorder[rooti])break;rooti++;}TreeNode* root=new TreeNode(postorder[i--]);root->right=_buildTree(inorder,postorder,i,rooti+1,end);root->left=_buildTree(inorder,postorder,i,begin,rooti-1);return root;}TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {int i=postorder.size()-1;TreeNode* root=_buildTree(inorder,postorder,i,0,inorder.size()-1);return root;}
};

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