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Problem

Reverse Bits

LeetCode #190Easy
build the answer bit by bit

Reverse the bits of an unsigned integer (the real problem is 32-bit; we use 8 bits here for clarity). 00101011 (43) becomes 11010100 (212).

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Build result bit by bit
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1result = 0
2repeat WIDTH times:
3  result = (result << 1) | (n & 1)  // pull lowest bit of n into result
4  n >>= 1                            // discard that bit
5return result
state
  • n43 = 00101011
  • result0 = 00000000
  • width8

line 1Reverse the order of the bits. Here n = 43 = 00101011 (8 bits for the animation; the real LeetCode problem is 32-bit). We will build the answer one bit at a time, reading n from its LOWEST bit.