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Problem

Number of 1 Bits

LeetCode #191Easy
Hamming weight · n & (n − 1)

Given an unsigned integer n, return the number of set bits (its Hamming weight).

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step 1 / 12
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[0][1][2][3]
Check each bit
▸
1count ← 0
2for i in 0..width-1:
3    count += (n >> i) & 1
4return count
state
  • n11
  • binary1011
  • count0

line 1n = 11 = 1011. The "Hamming weight" is just how many bits are 1. Simplest plan: look at every bit position, one at a time, and tally the 1s. Start count = 0.