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。
示例1
输入
[1,2,3,4,5,6,7],[3,2,4,1,6,5,7]
返回值
{1,2,5,3,4,6,7}
前序+中序->层序
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
TreeNode* build(int t,int l,int r,vector<int> pre,vector<int> vin)
{
if(l>r) return NULL;
if(l==r) return new TreeNode(pre[t]);
TreeNode* root=new TreeNode(pre[t]);
int i;
for(i=l;i<=r;i++)
if(vin[i]==pre[t])
break;
root->left=build(t+1,l,i-1,pre,vin);
root->right=build(t+i-l+1,i+1,r,pre,vin);
return root;
}
public:
TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> vin) {
return build(0,0,vin.size()-1,pre,vin);
}
};