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。
C++代码
/**
* 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.size() == 0 || vin.size() == 0) return NULL;
int val = pre[0];
TreeNode* root = new TreeNode(val);
int idx_root = -1;
for(int idx = 0;idx < vin.size(); idx++){
if (vin[idx] == val){
idx_root = idx;
break;
}
}
int left_node_cnt = idx_root - 0;
int right_node_cnt = vin.size() - 1 - idx_root;
if (left_node_cnt != 0){
vector<int> pre_t(pre.begin()+1,pre.begin()+left_node_cnt+1);
vector<int> vin_t(vin.begin(),vin.begin()+left_node_cnt);
root->left = reConstructBinaryTree(pre_t,vin_t);
}
if (right_node_cnt != 0){
vector<int> pre_t(pre.begin()+1+left_node_cnt,pre.end());
vector<int> vin_t(vin.begin() + idx_root + 1,vin.end());
root->right = reConstructBinaryTree(pre_t,vin_t);
}
return root;
}
};
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