LintCode2016年算法比赛----二叉树的所有路径

二叉树的所有路径

给定一棵二叉树，找从根节点到叶子节点的所有路径

样例

给出下面这课二叉树：

1
/   \
2     3
\
5

所有根到叶子的路径为：

[
"1->2->5",
"1->3"
]

算法分析：

递归地处理二叉树，先将子树的所有路径求出，然后把根节点的数据贴到子路径的所有结果上

/**
* Definition of TreeNode:
* public class TreeNode {
*     public int val;
*     public TreeNode left, right;
*     public TreeNode(int val) {
*         this.val = val;
*         this.left = this.right = null;
*     }
* }
*/
public class Solution {
/**
* @param root the root of the binary tree
* @return all root-to-leaf paths
*/
public List<String> binaryTreePaths(TreeNode root) {
// Write your code here
List<String>list=new ArrayList<>();
if(root!=null){
List<String>left=binaryTreePaths(root.left);
List<String>right=binaryTreePaths(root.right);
String current=String.valueOf(root.val);
if(left.size()==0&&right.size()==0){
list.add(current);
}
else{
if(left.size()!=0){
for(String leftStr:left){
list.add(current+"->"+leftStr);
}
}
if(right.size()!=0){
for(String rightStr:right){
list.add(current+"->"+rightStr);
}
}
}
}
return list;
}

}