考点:
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。
解题:
/**
* 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) {
if(pre.empty() || vin.empty()){
return NULL;
}
vector<int> pre_left,pre_right,vin_left,vin_right;
int pos = 0;
for( ;pos<vin.size();pos++){
if(vin[pos] == pre[0])
break;
}
TreeNode *root = new TreeNode(pre[0]);
for(int i=0;i<vin.size();i++){
if(i < pos){
vin_left.push_back(vin[i]);
pre_left.push_back(pre[i+1]);
}else if(i > pos){
vin_right.push_back(vin[i]);
pre_right.push_back(pre[i]);
}
}
root->left = reConstructBinaryTree(pre_left,vin_left);
root->right = reConstructBinaryTree(pre_right,vin_right);
return root;
}
};