Python · Theory

Second largest

Theory

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Second largest

Second largest is a classic practice problem. State the rule, trace a tiny input, then code. Fibonacci: next = sum of last two. Second largest: watch duplicates. Hanoi: move n-1, biggest, n-1. Distance: sqrt((x2-x1)**2 + (y2-y1)**2).

For Second largest — say the output for one small n before you write the loop. That is the exam.

Second largest — output — 8. Unique sorted → 1,3,8,9. Second last is 8, not 9 again.

Exam tip

Rule + one dry-run + then code.

Example

# Second largest
a = [9, 1, 9, 8, 3]
u = sorted(set(a))
print(u[-2])

Second largest — output: 8. Unique sorted → 1,3,8,9. Second last is 8, not 9 again.

Short notes

DefSecond largest — know the rule.
RuleSecond largest — tiny trace first.
RememberSecond largest — edge cases (n=0, duplicates).

Python · Theory

Second largest

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Theory

109/268

Second largest

For Second largest — say the output for one small n before you write the loop. That is the exam.

Second largest — output — 8. Unique sorted → 1,3,8,9. Second last is 8, not 9 again.

Exam tip

Rule + one dry-run + then code.

Example

# Second largest
a = [9, 1, 9, 8, 3]
u = sorted(set(a))
print(u[-2])

Second largest — output: 8. Unique sorted → 1,3,8,9. Second last is 8, not 9 again.

Short notes

DefSecond largest — know the rule.
RuleSecond largest — tiny trace first.
RememberSecond largest — edge cases (n=0, duplicates).

Second largest

Example

Short notes

Questions

Second largest

Example

Short notes

Questions