重建二叉树
题目描述
输入某二叉树的前序遍历和中序遍历的结果,请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6},则重建二叉树并返回。
/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> vin) { int len=vin.size(); if(len==0) return NULL; TreeNode* root=new TreeNode(pre[0]); vector<int> pre_left,pre_right,vin_left,vin_right; int rootpoint; for(int i=0; i<len; i++) { if(vin[i]==pre[0]) rootpoint=i; } for(int i=0; i<rootpoint; i++) { vin_left.push_back(vin[i]); pre_left.push_back(pre[i+1]); } for(int j=rootpoint+1; j<len; j++) { vin_right.push_back(vin[j]); pre_right.push_back(pre[j]); } root->left=reConstructBinaryTree(pre_left,vin_left); root->right=reConstructBinaryTree(pre_right,vin_right); return root; } void pre(TreeNode* &root) { if(root==NULL) return; cout<<root->val<<" "; pre(root->left); pre(root->right); } };