标签：style blog http os io strong for ar art
OJ: https://oj.leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/
Given inorder and postorder traversal of a tree, construct the binary tree.
Note: You may assume that duplicates do not exist in the tree.
思想： 迭代。
说明： 这类问题，要求一个提供根节点，然后另一个序列（中序序列）可依据根节点分出左右子树。
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
TreeNode *createTree(vector<int> &inorder, int start, int end, vector<int> &postorder, int start2, int end2) {
if(start > end || start2 > end2) return NULL;
TreeNode *root = new TreeNode(postorder[end2]);
int i;
for(i = start; i <= end; ++i)
if(inorder[i] == postorder[end2]) break;
// if(i > end) throws std::exception("error");
root->left = createTree(inorder, start, i-1, postorder, start2, start2 + i-start-1);
root->right = createTree(inorder, i+1, end, postorder, start2+i-start, end2-1);
return root;
}
class Solution {
public:
TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
return createTree(inorder, 0, inorder.size()-1, postorder, 0, postorder.size()-1);
}
};
Given preorder and inorder traversal of a tree, construct the binary tree.
Note: You may assume that duplicates do not exist in the tree.
思想： 同上。
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
TreeNode* createTree(vector<int> &preorder, int start, int end, vector<int> &inorder, int start2, int end2) {
if(start > end || start2 > end2) return NULL;
TreeNode *root = new TreeNode(preorder[start]);
int i;
for(i = start2; i <= end2; ++i)
if(preorder[start] == inorder[i]) break;
root->left = createTree(preorder, start+1, start+i-start2, inorder, start2, i-1);
root->right = createTree(preorder, start+i-start2+1, end, inorder, i+1, end2);
return root;
}
class Solution {
public:
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
return createTree(preorder, 0, preorder.size()-1, inorder, 0, inorder.size()-1);
}
};
标签：style blog http os io strong for ar art
原文地址：http://www.cnblogs.com/liyangguang1988/p/3940068.html
