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] ]
要寫出路徑和滿足要求的所有路徑 典型的回溯法遞歸求解 代碼如下:
public class Solution {
public List<List<Integer>> pathSum(TreeNode root, int sum) {
List<List<Integer>> res=new ArrayList<List<Integer>>(0);
List<Integer> tmp=new ArrayList<Integer>();
pathsearch(res, tmp, sum, 0, root);
return res;
}
public void pathsearch(List<List<Integer>> res,List<Integer> tmp,int sum,int cur,TreeNode root){
if(root==null)return;
List<Integer> ntmp=new ArrayList<Integer>();
ntmp.addAll(tmp);
ntmp.add(root.val);
if(root.left==null&&root.right==null){
if(sum==cur+root.val){
res.add(ntmp);
}
return;
}
if(root.left!=null){
pathsearch(res, ntmp, sum, cur+root.val, root.left);
}
if(root.right!=null){
pathsearch(res, ntmp, sum, cur+root.val, root.right);
}
}
}