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。

思路

核心思路是找出根节点，然后把左子树和右子树看成整体，继续寻找根节点，直到结束。运用迭代的方法实现。

/**
* 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) {
vect
4000
or<int> pre_left, pre_right, vin_left, vin_right;
int vin_length = vin.size();
int location = 0;

if(vin.size() == 0)
return NULL;

TreeNode* res = new TreeNode(pre[0]);
for(int i = 0; i < vin_length; i++){
if(vin[i] == pre[0])
location = i;
}

for(int i = 0; i < location; i++){
pre_left.push_back(pre[i+1]);
vin_left.push_back(vin[i]);
}

for(int i = location+1; i < vin_length; i++){
pre_right.push_back(pre[i]);
vin_right.push_back(vin[i]);
}

res->left = reConstructBinaryTree(pre_left, vin_left);
res->right = reConstructBinaryTree(pre_right, vin_right);

return res;
}
};