Construct Binary Tree from Preorder and Inorder Traversal

题目名称

105. Construct Binary Tree from Preorder and Inorder Traversal

描述

Given preorder and inorder traversal of a tree, construct the binary tree.

分析

  详细分析过程见我的博客二叉树——根据二叉树遍历序列构造二叉树

C++代码

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
return create(preorder,inorder,
0,preorder.size()-1,0,inorder.size()-1);
}

TreeNode* create(vector<int>& preorder,vector<int>& inorder,int pl,int pr,int il,int ir) {
if(pl>pr) return nullptr;
TreeNode* node = new TreeNode(preorder[pl]);
int pos;
for(int i = il;i<=ir;i++) {
if(inorder[i] == node->val){
pos = i;
break;
}
}

node->left = create(preorder,inorder,pl+1,pl+pos-il,il,pos-1);
node->right = create(preorder,inorder,pl+pos-il+1,pr,pos+1,ir);

return node;
}
};