problem:
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]
]
Hide Tags Tree Depth-first Search 題意:在二叉樹根節點到葉子節點的所有路徑上,如果路徑節點數值之和為特定數sum,輸出所有滿足該條件的路徑
thinking:
是上道題的變形,DFS周遊所有孩子節點,并記錄路徑和。到達葉子節點時(左右孩子為空)判斷是否為有效路徑,有效則儲存該路徑。
code:
class Solution {
private:
vector<vector<int> > ret;
public:
vector<vector<int> > pathSum(TreeNode *root, int sum) {
ret.clear();
vector<int> path;
if(root==NULL)
return ret;
dfs(0,sum,path,root);
return ret;
}
protected:
void dfs(int add, int sum, vector<int> path,TreeNode *node)
{
path.push_back(node->val);
add+=node->val;
if(node->left==NULL && node->right==NULL)
{
if(add==sum)
ret.push_back(path);
return;
}
if(node->left!=NULL)
dfs(add,sum,path,node->left);
if(node->right!=NULL)
dfs(add,sum,path,node->right);
}
};