71 lines
1.3 KiB
Markdown
71 lines
1.3 KiB
Markdown
---
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layout: page
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title: Path Sum 2
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last_solved:
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category: tree
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leetcode_url: https://leetcode.com/problems/path-sum-ii/
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status: Attempted
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---
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Problem
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-------
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```
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Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.
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Note: A leaf is a node with no children.
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Example:
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Given the below binary tree and sum = 22,
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5
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/ \
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4 8
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/ / \
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11 13 4
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/ \ / \
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7 2 5 1
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Return:
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[
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[5,4,11,2],
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[5,8,4,5]
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]
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```
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Solution
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----------
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Use dfs helper to pass down currentSum. Check if leaf node and sumTotal==targetSum.
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{% highlight python %}
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def dfs(node, currentSum, targetSum, path):
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if not node:
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return
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# if current node is leaf and sum of all vals == targetSum
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if node.left is None and node.right is None and currentSum + node.val == targetSum:
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output.append(path+[node.val])
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leftRes = dfs(node.left, currentSum + node.val, targetSum, path+[node.val])
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rightRes = dfs(node.right, currentSum + node.val, targetSum, path+[node.val])
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return
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output = []
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dfs(root, 0, sum, [])
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return output
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{% endhighlight %}
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_______________
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{% highlight python %}
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{% endhighlight %} |