Construct String from Binary Tree
给一个数组, 返回有括号表示后的pre order traversing..
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public String tree2str(TreeNode t) {
if(t == null)
return "";
String right = tree2str(t.right);
String left = tree2str(t.left);
String res = t.val+"";
if(right.equals("") && left.equals(""))
return res;
else if(right.equals("")){
return res + "(" + left + ")";
}
else
return res + "(" + left + ")" + "(" + right + ")";
}
}