**Subject description:**

And enter the result in a preorder traversal of a binary tree in preorder traversal of the binary tree a rebuild. Suppose Results preorder traversal order and input of duplicate numbers are free. Before entering e.g. preorder traversal sequence {1,2,4,7,3,5,6,8} and {4,7,2,1,5,3,8,6} order traversal sequence, and the reconstructed binary tree return.

public class Solution { class TreeNode { int val; TreeNode left; TreeNode right; TreeNode(int x) { val = x; } } public TreeNode reConstructBinaryTree(int[] pre, int[] in) { if (pre != null && in != null) return solution(pre, in, 0, pre.length - 1, 0, in.length - 1); else return null; } private TreeNode solution(int[] pre, int[] in, int pStart, int pEnd, int iStart, int iEnd) { if (pStart > pEnd || iStart > iEnd) return null; TreeNode tree = new TreeNode(pre[pStart]); for (int root = iStart; root <= iEnd; root++) if (in[root] == pre[pStart]) { int leftLen = root - iStart; tree.left = solution(pre, in, pStart + 1, pStart + leftLen, iStart, root - 1); tree.right = solution(pre, in, pStart + leftLen + 1, pEnd, root + 1, iEnd); break; } return tree; } }