Path Sum II leetcode java

1895 ワード
LeetCode
タイトル:
Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example:
Given the below binary tree and sum = 22 , 
              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return 
[
   [5,4,11,2],
   [5,8,4,5]
]

  ： 
                path sum，                ，       DFS       。    ：
 1     
public 
void pathSumHelper(TreeNode root, 
int sum, List  sumlist, List> pathlist){
 2         
if(root==
null) 
 3             
return;
 4         sumlist.add(root.val);
 5         sum = sum-root.val;
 6         
if(root.left==
null && root.right==
null){
 7             
if(sum==0){
 8                 pathlist.add(
new ArrayList(sumlist));
 9             }
10         }
else{
11             
if(root.left!=
null)
12                 pathSumHelper(root.left,sum,sumlist,pathlist);
13             
if(root.right!=
null)
14                 pathSumHelper(root.right,sum,sumlist,pathlist);
15         }
16         sumlist.remove(sumlist.size()-1);
17     }
18     
19     
public List> pathSum(TreeNode root, 
int sum) {
20         List> pathlist=
new ArrayList>();
21         List sumlist = 
new ArrayList();
22         pathSumHelper(root,sum,sumlist,pathlist);
23         
return pathlist;
24     }

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