[Solved] Suppose the Path Sum problem is modified so that node values can be negative, and you want to find if any... Which of the following changes to the DFS approach is necessary to handle this correctly? | Tree: Depth-First Search

Tree: Depth-First Search - Path Sum

Suppose the Path Sum problem is modified so that node values can be negative, and you want to find if any root-to-leaf path sums exactly to targetSum. Which of the following changes to the DFS approach is necessary to handle this correctly?

APrecompute all path sums and store them in a hash set for O(1) lookup

BAdd memoization to avoid revisiting nodes with the same current sum

CUse BFS instead of DFS to guarantee shortest path sum

DRemove early stopping because negative values can invalidate pruning assumptions

Step-by-Step Solution

Step 1: Understand impact of negative values
Negative values mean partial sums can decrease later, so pruning based on current sum is unsafe.
Step 2: Adjust algorithm accordingly
Early stopping based on partial sums must be removed to avoid missing valid paths.
Final Answer:
Option D -> Option D
Quick Check:
Negative values break pruning assumptions, so early stopping must be disabled [OK]

Quick Trick: Negative values invalidate pruning, so no early stopping [OK]

Common Mistakes:

MISTAKES

Assuming early stopping always works
Switching to BFS unnecessarily

Trap Explanation:

PITFALL

Early stopping looks efficient but fails with negative values; memoization or BFS don't solve pruning issues here.

Interviewer Note:

CONTEXT

Tests candidate's understanding of pruning assumptions and algorithm robustness.

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Which of the following changes to the DFS approach is necessary to handle this correctly?

Step 1: Understand impact of negative values

Step 2: Adjust algorithm accordingly

Final Answer:

Quick Check:

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