识别信号
- They expect you to replace repeated subtraction with doubling or left shifts, not brute force loops.
- They are checking whether you know why INT_MIN cannot be safely negated in 32-bit signed arithmetic.
- Clarifies whether negative numbers and zero should return false.
解题流程
- 1. 明确窗口/状态定义
- 2. 更新状态并维护约束
- 3. 用边界样例验证
常见失分点
- Taking abs(INT_MIN) in a 32-bit type and silently overflowing before the real logic even starts.
- Not handling zero and negative inputs correctly, returning true incorrectly.
- Checking only n > 0 or n & (n - 1) without verifying bit position can misidentify powers of two as powers of four.
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