[剑指offer] 重建二叉树

/**
 * 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) {
        if(pre.length ==0 || in.length == 0)
            return null;
        return ConstructBinaryTree(pre, 0, pre.length - 1, in, 0, in.length - 1);
    }

    public TreeNode ConstructBinaryTree(int [] pre, int ps, int pe, 
int [] in, int is, int ie){
        if(ps > pe || is > ie){
            return null;
        }
        TreeNode root = new TreeNode(pre);
        for(int i = is; i<=ie; i++){
            if(in[i] == pre){
                root.left = ConstructBinaryTree(pre, ps+1, ps+i-is, in, is, i-1);
                root.right = ConstructBinaryTree(pre, ps+i-is+1, pe, in, i+1, ie);
                break;
            }
        }
        return root;
    }
}