输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。
前序：{1,2,4,7,3,5,6,8}，前序的第一个一定是根节点，所以1是根节点
中序：{4,7,2,1,5,3,8,6}，1的左边是左子树，1的右边是右子树
Solution1:
public class Solution {
public TreeNode reConstructBinaryTree(int[] pre,int[] in) {
TreeNode root = reConstructBinaryTree(pre, 0, pre.length - 1, in, 0, in.length - 1);
return root;
}
private TreeNode reConstructBinaryTree(int[] pre, int pStart, int pEnd, int[] in, int iStart, int iEnd) {
if (pStart > pEnd || iStart > iEnd) {
return null;
}
TreeNode root = new TreeNode(pre[pStart]);
int index = 0;
for (int i = iStart; i <= iEnd; i++) {
if (in[i] == pre[pStart]) {
index = i;
}
}
int length = index - iStart;
root.left = reConstructBinaryTree(pre, pStart + 1, pStart + length, in, iStart, index - 1);
root.right = reConstructBinaryTree(pre, pStart + length + 1, pEnd, in, index + 1, iEnd);
return root;
}
}
