Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.

Note:

You may assume that duplicates do not exist in the tree.
根据前序遍历和中序遍历构建树。

public:
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

return build(preorder,inorder,0,preorder.size()-1,0,inorder.size()-1);
}

TreeNode *build(vector<int> &preorder, vector<int> &inorder,int s1,int e1,int s2,int e2)
{
if(s1 > e1 || s2 > e2) return NULL;

vector<int>::iterator it = find(inorder.begin(),inorder.end(),preorder[s1]);
int index = it - inorder.begin();

TreeNode *root = new TreeNode(preorder[s1]);
TreeNode *left = build(preorder,inorder,s1+1,s1+index - s2,s2,index-1);
TreeNode *right = build(preorder,inorder,s1+index - s2+1,e1,index+1,e2);

root->left = left;
root->right = right;
return root;
}
};

148 milli secs