/**

* @author libingc

* @date 2020/11/23

*/

//从前序和中序序列构建二叉树

public class buildTree {

public TreeNode Solution(int[] preorder, int[] inorder) {

return buildTreeHelper(preorder, inorder, (long)Integer.MAX_VALUE + 1);

}

int pre = 0;

int in = 0;

private TreeNode buildTreeHelper(int[] preorder, int[] inorder, long stop) {

//terminator

if(pre == preorder.length){

return null;

}

if (inorder[in] == stop) {

in++;

return null;

}

//process

int root_val = preorder[pre++];

TreeNode root = new TreeNode(root_val);

//drill down

root.left = buildTreeHelper(preorder, inorder, root_val);

root.right = buildTreeHelper(preorder, inorder, stop);

return root;

}

}