剑指offer——重建二叉树

/**
* 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) {
int inlen = vin.size();
if(inlen==0)
return NULL;
//创建根节点，肯定是前序遍历的第一个节点
TreeNode* root=new TreeNode(pre[0]);
vector<int> left_pre,left_vin,right_pre,right_vin;
//在中序遍历中找到根节点
int gen = 0;
for(int i=0;i<inlen;i++) {
if(vin[i]==pre[0]) {
gen = i;
break;
}
}
//构建左右子树的前序遍历和中序遍历
for(int i=0;i<gen;i++) {
left_pre.push_back(pre[i+1]);
left_vin.push_back(vin[i]);
}
for(int i=gen+1;i<inlen;i++) {
right_pre.push_back(pre[i]);
right_vin.push_back(vin[i]);
}
root->left = reConstructBinaryTree(left_pre,left_vin);
root->right = reConstructBinaryTree(right_pre,right_vin);

return root;
}
};