Greedy Algorithms - Largest Number (Arrange to Form Biggest)
Consider the following Python code for forming the largest number from the list [3, 30, 34, 5]. What is the final returned string?
Consider the following Python code for forming the largest number from the list [3, 30, 34, 5]. What is the final returned string?
easy🧾 Code Trace Q12 of Q15
Step-by-Step Solution
Solution:
Step 1: Convert numbers to strings: ['3', '30', '34', '5']
We compare pairs by concatenation: '5'+'34' vs '34'+'5' -> '534' > '345', so '5' before '34'. Similarly for others.Step 2: Sort using custom comparator to get order: ['5', '34', '3', '30']
Concatenate to get '534330'. The check for leading zero is false since first is '5'.Final Answer:
Option A -> Option AQuick Check:
Concatenation order matches expected largest number [OK]
Quick Trick: Compare concatenations 'a+b' and 'b+a' to order strings [OK]
Common Mistakes:
MISTAKES- Off-by-one in sorting
- Ignoring leading zero case
- Misordering '30' and '3'
Trap Explanation:
PITFALL- Candidates often confuse numeric vs string comparison or forget to compare concatenations both ways.
Interviewer Note:
CONTEXT- Tests ability to mentally execute custom comparator sorting
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