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https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversa
`/**
https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal
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& preorder, vector& inorder) { //数据合法性检验 if (preorder.size() != inorder.size()) return NULL;
//递归构造一颗树 return helper(preorder, 0,preorder.size()-1, \ inorder,0,inorder.size()-1);
}
TreeNode* helper(vector& preorder,int pStart,int pEnd,vector& inorder,int iStart,int iEnd) { //cout<< pEnd << " "<< pStart << " " <<iEnd << iStart<<endl;
if (pEnd < pStart || iEnd < iStart) { return NULL; } TreeNode* root =new TreeNode(preorder[pStart]); //根据preorder[pStart]拆分左右子树,并且计算范围 int mid=iStart ; // while (inorder[iStart] != root->val) //iStart 位置不能发生变化,变化的mid while (inorder[mid] != root->val) { mid++; } int left = mid-iStart; //对各自范围构造一棵树 root->left = helper(preorder,pStart+1,pStart+left,inorder,iStart,mid-1); root->right = helper(preorder,pStart+left+1,pEnd,inorder,mid+1,iEnd); return root;
};`
Activity
watchpoints commentedon Aug 7, 2019
https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversa
watchpoints commentedon Aug 7, 2019
`/**
https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal
Definition for a binary tree node.
struct TreeNode {
};
/
class Solution {
public:
TreeNode buildTree(vector& preorder, vector& inorder) {
//数据合法性检验
if (preorder.size() != inorder.size()) return NULL;
}
TreeNode* helper(vector& preorder,int pStart,int pEnd,vector& inorder,int iStart,int iEnd)
{ //cout<< pEnd << " "<< pStart << " " <<iEnd << iStart<<endl;
}
};`