剑指offer——面6：重建二叉树

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

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        return reconTree(pre,0,pre.length-1,in,0,in.length-1);
    }
    public TreeNode reconTree(int[] pre,int lowP,int highP,int[] in,int lowI,int highI){
        if(lowP>highP||lowI>highI)
            return null;
        TreeNode root=new TreeNode(pre[lowP]);
        for(int i=lowI;i<=highI;i++){
            if(pre[lowP]==in[i]){
                root.left=reconTree(pre,lowP+1,lowP+i-lowI,in,lowI,i-1);
                root.right=reconTree(pre,lowP+i-lowI+1,highP,in,i+1,highI);
                break;
            }
        }
        return root;
    }
}
//运行时间：383ms占用内存：22848k

注意：递归时的条件（多次犯错的部分）