Greedy Algorithms - Largest Number (Arrange to Form Biggest)
Given the input list [9, 91, 90], what is the output of the largest number formation algorithm that sorts numbers as strings with a custom comparator?
Given the input list [9, 91, 90], what is the output of the largest number formation algorithm that sorts numbers as strings with a custom comparator?
easy🧾 Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Convert numbers to strings
Strings: "9", "91", "90"Step 2: Compare pairs using concatenation
Compare "9"+"91" = "991" vs "91"+"9" = "919"; "991" > "919", so "9" > "91"Step 3: Compare "91" and "90"
"91"+"90" = "9190" vs "90"+"91" = "9091"; "9190" > "9091", so "91" > "90"Step 4: Sorted order is ["9", "91", "90"]
Concatenate to get "99190"Final Answer:
Option A -> Option AQuick Check:
Concatenation comparisons confirm order [OK]
Quick Trick: Compare xy and yx concatenations to decide order [OK]
Common Mistakes:
MISTAKES- Sorting numerically descending ignoring concatenation
- Assuming longer strings always come first
- Mixing up concatenation order in comparisons
Trap Explanation:
PITFALL- Ignoring concatenation order leads to incorrect output.
Interviewer Note:
CONTEXT- Tests ability to trace the sorting logic step-by-step.
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