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6 Perfect Square

Problem Statement

Write a Recursive Solution to Check if a Given Number is a Perfect Square or Not.

The problem is to determine whether a given positive number is a perfect square or not. A square number or perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself.

Examples

InputOutputExplanation
16True16 is a perfect square because 4 * 4 = 16.
14False14 is not a perfect square because there is no integer whose square is equal to 14.
9True9 is a perfect square because 3 * 3 = 9.

Constraints:

Try it yourself

Try solving this question here:

🎯 STRICT STANDOUT — Problem cue: Perfect Square

1. Why

Find i with i²=n. Linear O(n); binary search on i is O(log n). Recursion optional on BS form.

2. Big-O (K11)

Linear i scan O(n); binary mid*mid vs n: O(log n); recursive BS stack O(log n)

3. Pattern + when-NOT

BINARY SEARCH ON ANSWER. When-NOT: recurse i=i+1 to n (O(n) stack).

4. Edge

0,1 true; 2 false; 16 true; 14 false; neg false; mid*mid overflow → long

5. Panel

Q: Why BS works? A: i² monotone for i≥0.

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📝 My notes