4. Bit Manipulation
AND, OR, XOR, shifts and the classic bit tricks.
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8easy
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0hard
Understand the topic
Every int is 32 switches. Bit manipulation means flipping and reading those switches directly with & (both on), | (either on), ^ (different), ~ (flip) and shifts (<< and >>).
Three tricks solve most problems here: x & (x - 1) removes the lowest 1-bit, x & -x keeps only the lowest 1-bit, and a ^ a = 0 makes pairs cancel out. In Java, use >>> to shift right without copying the sign bit.
| # | Problem | Pattern | Level | ||
|---|---|---|---|---|---|
| 1 | Number of 1 Bits #191 | n & (n-1) | Easy | LeetCode ↗ | |
| 2 | Power of Two #231 | n & (n-1) | Easy | LeetCode ↗ | |
| 3 | Single Number #136 | XOR | Easy | LeetCode ↗ | |
| 4 | Counting Bits #338 | Bits + DP | Easy | LeetCode ↗ | |
| 5 | Missing Number #268 | XOR | Easy | LeetCode ↗ | |
| 6 | Reverse Bits #190 | Shifts | Easy | LeetCode ↗ | |
| 7 | Hamming Distance #461 | XOR + popcount | Easy | LeetCode ↗ | |
| 8 | Complement of Base 10 Integer #1009 | Bit masks | Easy | LeetCode ↗ | |
| 9 | Single Number II #137 | Bit counting | Medium | LeetCode ↗ | |
| 10 | Single Number III #260 | XOR + lowest set bit | Medium | LeetCode ↗ | |
| 11 | Sum of Two Integers #371 | XOR + carry | Medium | LeetCode ↗ | |
| 12 | Bitwise AND of Numbers Range #201 | Common prefix | Medium | LeetCode ↗ |
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Work top to bottom — each list goes from easy to hard. Try a problem for at least 15 minutes before opening a hint. Ticks are saved in your browser.