LeetCode offer 07. c++ 经典数组重建二叉树,熟练
原题链接
中等
作者:
大明湖的鱼
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2021-01-27 12:53:58
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所有人可见
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阅读 333
/**
* 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>& preorder, vector<int>& inorder) {
return build(preorder,inorder,0,0,inorder.size()-1);
}
TreeNode* build(vector<int>& preorder,vector<int>& inorder,int root,int start,int end){//中序的start和end
if(start > end) return nullptr;
auto tree = new TreeNode(preorder[root]);
int i = start;
while(i < end && preorder[root] != inorder[i]) i++;
tree->left = build(preorder,inorder,root+1,start,i-1);
tree->right = build(preorder,inorder,root+1+i-start,i+1,end);
return tree;
}
};
#### 由中序和后序建树,关键是背下来 l 和 r 的范围,