标签：push array while node c++ empty amp example highlight
Given a binary tree and a sum, find all root-to-leaf paths where each path‘s sum equals the given sum.
Note: A leaf is a node with no children.
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] ]
Approach #1: C++. [Recursive]
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int>> pathSum(TreeNode* root, int sum) {
if (root == NULL) return ans;
vector<int> temp;
helper(root, temp, 0, sum);
return ans;
}
private:
vector<vector<int>> ans;
void helper(TreeNode* root, vector<int> temp, int cur, int sum) {
if (root == NULL) return;
temp.push_back(root->val);
if (root->left == NULL && root->right == NULL && cur+root->val == sum) {
ans.push_back(temp);
return;
}
helper(root->left, temp, cur+root->val, sum);
helper(root->right, temp, cur+root->val, sum);
}
};
Approach #2: Java.[DFS+Stack]
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<List<Integer>> pathSum(TreeNode root, int sum) {
List<List<Integer>> res = new ArrayList<>();
List<Integer> path = new ArrayList<>();
Stack<TreeNode> stack = new Stack<>();
int curSum = 0;
TreeNode cur = root;
TreeNode prev = null;
while (cur != null || !stack.isEmpty()) {
while (cur != null) {
stack.push(cur);
curSum += cur.val;
path.add(cur.val);
cur = cur.left;
}
cur = stack.peek();
if (cur.right != null & cur.right != prev) {
cur = cur.right;
continue;
}
if (cur.left == null && cur.right == null && curSum == sum)
res.add(new ArrayList<Integer>(path));
prev = cur;
stack.pop();
path.remove(path.size()-1);
curSum -= cur.val;
cur = null;
}
return res;
}
}
Approach #3: Python. [BFS+Queue]
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def pathSum(self, root, sum):
"""
:type root: TreeNode
:type sum: int
:rtype: List[List[int]]
"""
if root == None:
return []
res = []
queue = [(root, root.val, [root.val])]
while queue:
curr, val, ls = queue.pop()
if not curr.left and not curr.right and val == sum:
res.append(ls)
if curr.left:
queue.append((curr.left, val+curr.left.val, ls+[curr.left.val]))
if curr.right:
queue.append((curr.right, val+curr.right.val, ls+[curr.right.val]))
return res
标签：push array while node c++ empty amp example highlight
原文地址：https://www.cnblogs.com/ruruozhenhao/p/10093284.html
