题目：
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。
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:
struct TreeNode* reConstructBinaryTree(vector<int> pre,vector<int> in) {
return build(pre.begin(), in.begin(), pre.size());
}
struct TreeNode* build(vector<int>::iterator pre_iter, vector<int>::iterator in_iter, int n){
if(n == 0) return NULL;
struct TreeNode *root = new TreeNode(*pre_iter);
int left, right, i;
for(i = 0; i < n && *(in_iter+i) != *pre_iter; i++);
left = i;
right = n - i - 1;
root->left = build(pre_iter+1, in_iter, left);
root->right = build(pre_iter+left+1, in_iter+left+1, right);
return root;
}
};
