[LeetCode] 113. Path Sum II 路径和 II

Posted 2020-10-27 轻风舞动

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]
]

112. Path Sum 的拓展，上一题只要求返回是否存在，这题要求输出具体的路径。

 Java:

/**
  * 和原来的不一样，这题要完全遍历，使用track跟踪当前的进度，进入dfs时压进去，出dfs时推出，当时叶节点且和正好为0是，克隆添加到结果中。
  * */
public class Solution {
    List<List<Integer>> list;
    LinkedList<Integer> track;
    public void dfs(TreeNode root,int sum){
        if(root==null)
            return;
        sum-=root.val;
        track.add(root.val);
        if(sum==0 && root.left==null && root.right==null)
            list.add((LinkedList<Integer>)track.clone());
        dfs(root.left,sum);
        dfs(root.right,sum);
        track.remove(track.size()-1);

    }
    public List<List<Integer>> pathSum(TreeNode root, int sum) {
        this.list=new ArrayList<List<Integer>>();
        this.track=new LinkedList<Integer>();
        dfs(root,sum);
        return this.list;
    }
}　　

Python:

class Solution:
    # @param root, a tree node
    # @param sum, an integer
    # @return a list of lists of integers
    def pathSum(self, root, sum):
        return self.pathSumRecu([], [], root, sum)

    
    def pathSumRecu(self, result, cur, root, sum):
        if root is None:
            return result
        
        if root.left is None and root.right is None and root.val == sum:
            result.append(cur + [root.val])
            return result
        
        cur.append(root.val)
        self.pathSumRecu(result, cur, root.left, sum - root.val)
        self.pathSumRecu(result, cur,root.right, sum - root.val)
        cur.pop()
        return result　　

C++:

class Solution {
public:
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        vector<vector<int>> res;
        vector<int> out;
        helper(root, sum, out, res);
        return res;
    }
    void helper(TreeNode* node, int sum, vector<int>& out, vector<vector<int>>& res) {
        if (!node) return;
        out.push_back(node->val);
        if (sum == node->val && !node->left && !node->right) {
            res.push_back(out);
        }
        helper(node->left, sum - node->val, out, res);
        helper(node->right, sum - node->val, out, res);
        out.pop_back();
    }
};

　　

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[LeetCode] 112. Path Sum 路径和

[LeetCode] 437. Path Sum III 路径和 III 

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