[leetcode刷题系列]Construct Binary Tree from Inorder and Postorder Traversal

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
TreeNode * dfs(int in_left, int in_right, vector<int> & inorder,
int post_left, int post_right, vector<int> & postorder){
if(in_left > in_right)
return 0;
TreeNode * ret = new TreeNode(postorder[post_right]);
for(int i = in_left; i <= in_right; ++ i)
if(inorder[i] == postorder[post_right]){
ret->left = dfs(in_left, i - 1, inorder, post_left, post_left + i - 1 - in_left, postorder);
ret->right = dfs(i + 1, in_right, inorder, post_right - 1 - (in_right - i - 1),post_right - 1, postorder);
return ret;
}
return 0;
}
public:
TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(inorder.size() <= 0)
return 0;
return dfs(0, inorder.size() - 1, inorder, 0, postorder.size() - 1, postorder);
}
};