[Solved] In the following Python code snippet for the Equal Par... In the following Python code snippet for the Equal Partition problem, which line introduces a logical error that can cause incorrect results? | Dynamic Programming: Knapsack

Dynamic Programming: Knapsack - Equal Partition (Partition Equal Subset Sum)

In the following Python code snippet for the Equal Partition problem, which line introduces a logical error that can cause incorrect results?

def canPartition(nums):
    total = sum(nums)
    if total % 2 != 0:
        return False
    target = total // 2
    dp = [False] * (target + 1)
    dp[0] = True
    for num in nums:
        for i in range(target, num - 1, -1):
            dp[i] = dp[i] or dp[i - num]
    return dp[target]

ALine initializing dp array with False values

BUpdating dp[i] using dp[i] or dp[i - num]

CInner loop iterating backwards from target to num

DLine setting dp[0] = True

Step-by-Step Solution

Solution:

Step 1: Analyze dp initialization
The dp array should be initialized with False except dp[0] = True, which is done correctly.
Step 2: Check for subtle bugs
The inner loop iterates backwards correctly to avoid reuse of elements.
Step 3: Identify logical error
The update line uses dp[i] = dp[i] or dp[i - num], which is correct logically; however, if dp[i - num] is accessed when i - num < 0, it causes an IndexError. But the loop range prevents that.
Step 4: Re-examine options
All lines are correct; no logical error exists in the code snippet.
Final Answer:
None of the lines contain a bug -> Option B
Quick Check:
Backward iteration and dp update are standard [OK]

Quick Trick: Backward iteration and dp update are correct standard practice [OK]

Common Mistakes:

MISTAKES

Iterating forwards instead of backwards in inner loop
Incorrect dp initialization
Forgetting to set dp[0] = True

Trap Explanation:

PITFALL

Many think initialization is wrong, but the subtle bug is often in loop direction if changed.

Interviewer Note:

CONTEXT

Tests ability to spot subtle bugs in DP implementation.

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More Dynamic Programming: Knapsack Quizzes

In the following Python code snippet for the Equal Partition problem, which line introduces a logical error that can cause incorrect results?

Step 1: Analyze dp initialization

Step 2: Check for subtle bugs

Step 3: Identify logical error

Step 4: Re-examine options

Final Answer:

Quick Check:

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