Tree: Depth-First Search - Path Sum III (Any Path)
Consider the same prefix sum DFS code as before. What is the output when the input tree has a single node with value 0 and targetSum = 0?
Consider the same prefix sum DFS code as before. What is the output when the input tree has a single node with value 0 and targetSum = 0?
medium🧾 Code Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace prefix sums for single node 0
Initial prefix_counts has {0:1}, current_sum=0+0=0, so result += prefix_counts[0-0]=1.Step 2: Count paths including single node only
Only one path (the single node itself) sums to 0.Final Answer:
Option D -> Option DQuick Check:
Single node zero with target zero yields 1 path [OK]
Quick Trick: Remember prefix_counts[0] = 1 counts empty path but empty path is not counted as a valid path here [OK]
Common Mistakes:
MISTAKES- Ignoring empty path count
- Assuming single node path counts once only
Trap Explanation:
PITFALL- Candidates often confuse empty path counting with valid path counting.
Interviewer Note:
CONTEXT- Tests handling of edge cases with zero values and empty path counting.
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