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106.cpp
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106.cpp
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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 bt(inorder, postorder, 0, 0, postorder.size());
}
TreeNode * bt(vector<int> & inorder, vector<int> & postorder, int ino, int post, int sz) {
if(sz == 0) return NULL;
else if(sz == 1) return new TreeNode(postorder[post]);
else {
int loc = ino;
for(int i = 0; i < sz; ++i) {
if(inorder[ino + i] == postorder[post + sz - 1]) {
loc = ino + i;
break;
}
}
TreeNode * res = new TreeNode(postorder[post + sz - 1]);
res->left = bt(inorder, postorder, ino, post, loc - ino);
res->right = bt(inorder, postorder, loc + 1, post + loc - ino, sz - 1 - loc + ino);
return res;
}
}
};