Question
Given inorder and postorder traversal of a tree, construct the binary tree.
Note:
You may assume that duplicates do not exist in the tree.
Solution
参考:http://www.cnblogs.com/zhonghuasong/p/7096300.html
Code
/**
* 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) {
if (inorder.size() == 0 || postorder.size() == 0)
return NULL;
return ConstructTree(inorder, postorder, 0, inorder.size() - 1, 0, postorder.size() - 1);
}
TreeNode* ConstructTree(vector<int>& inorder, vector<int>& postorder,
int in_start, int in_end, int post_start, int post_end) {
int rootValue = postorder[post_end];
TreeNode* root = new TreeNode(rootValue);
if (in_start == in_end) {
if (post_start == post_end && inorder[in_start] == postorder[post_start])
return root;
}
int rootIn = in_start;
while (rootIn <= in_end && inorder[rootIn] != rootValue)
rootIn++;
int leftPostLength = rootIn - in_start;
if (leftPostLength > 0) {
// 注意起点和终点的写法
root->left = ConstructTree(inorder, postorder, in_start, rootIn - 1, post_start, post_start + leftPostLength - 1);
}
if (leftPostLength < in_end - in_start) {
root->right = ConstructTree(inorder, postorder, rootIn + 1, in_end, post_start + leftPostLength, post_end - 1);
}
return root;
}
};