二叉树重建

class {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        return reConstructBinaryTree(pre,0,pre.length-1,in,0,in.length-1);
    }
private TreeNode reConstructBinaryTree(int [] pre,int startPre,int endPre,int [] in,int startIn,int endIn){
        if(startPre > endPre || startIn > endIn) return null;
        TreeNode root = new TreeNode(pre[startPre]);
        for(int i = startIn; i<= endIn ; i++){
            if(in[i] == pre[startPre]){
                root.left=reConstructBinaryTree(pre,startPre+1,startPre+i-startIn,in,startIn,i-1);
                root.right=reConstructBinaryTree(pre,i-startIn+startPre+1,endPre,in,i+1,endIn);
                break;
            }
        }
        return root;
    }