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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
return buildSubTree(inorder, postorder, 0, inorder.size()-1, 0, postorder.size()-1);
}
TreeNode* buildSubTree(vector<int>& inorder, vector<int>& postorder, int in_left, int in_right, int post_left, int post_right)
{
if(in_left > in_right || post_left > post_right)
return NULL;
else if(in_left == in_right || post_left == post_right)
{
TreeNode* new_node = new TreeNode(postorder[post_right]);
return new_node;
}
else
{
TreeNode* new_node = new TreeNode(postorder[post_right]);
int i = in_left;
for(; i <= in_right; i++)
{
if(inorder[i] == postorder[post_right])
break;
}
int new_position = i;
int right_length = in_right-new_position;
new_node->left = buildSubTree(inorder, postorder, in_left, new_position-1, post_left, post_right-right_length-1);
new_node->right = buildSubTree(inorder, postorder, new_position+1, in_right, post_right-right_length, post_right-1);
return new_node;
}
}
};
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