[Solved] Suppose the problem is modified so that node values can be negative, and you want to find all root-to-leaf paths summing... Which modification to the DFS approach is necessary to ensure correctness? | Tree: Depth-First Search

Tree: Depth-First Search - Path Sum II (All Root-to-Leaf Paths)

Suppose the problem is modified so that node values can be negative, and you want to find all root-to-leaf paths summing to targetSum. Which modification to the DFS approach is necessary to ensure correctness?

ARemove pruning and explore all paths fully since negative values can reduce sums

BAdd pruning to stop exploring paths when current_sum exceeds targetSum

CUse BFS instead of DFS to avoid infinite loops caused by negative values

DSort children nodes by value to explore promising paths first

Step-by-Step Solution

Solution:

Step 1: Understand effect of negative values
Negative values can decrease current_sum, so pruning based on exceeding targetSum can miss valid paths.
Step 2: Adjust DFS to remove pruning
To ensure all valid paths are found, pruning must be removed and all paths fully explored.
Final Answer:
Option A -> Option A
Quick Check:
Pruning breaks correctness with negative values; full exploration needed [OK]

Quick Trick: Negative values invalidate pruning based on sum limits [OK]

Common Mistakes:

MISTAKES

Applying pruning blindly
Switching to BFS unnecessarily

Trap Explanation:

PITFALL

Pruning looks efficient but breaks correctness with negative values

Interviewer Note:

CONTEXT

Tests understanding of pruning limitations and negative value impact

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More Tree: Depth-First Search Quizzes

Which modification to the DFS approach is necessary to ensure correctness?

Step 1: Understand effect of negative values

Step 2: Adjust DFS to remove pruning

Final Answer:

Quick Check:

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