# Number Of 1 Bits Problem

## Description

LeetCode Problem 191.

Write a function that takes an unsigned integer and returns the number of ‘1’ bits it has (also known as the Hamming weight).

Note:

• Note that in some languages, such as Java, there is no unsigned integer type. In this case, the input will be given as a signed integer type. It should not affect your implementation, as the integer’s internal binary representation is the same, whether it is signed or unsigned.
• In Java, the compiler represents the signed integers using 2’s complement notation. Therefore, in Example 3, the input represents the signed integer. -3.

Example 1:

``````1
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Input: n = 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.
``````

Example 2:

``````1
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Input: n = 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.
``````

Example 3:

``````1
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Input: n = 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.
``````

Constraints:

• The input must be a binary string of length 32.

## Sample C++ Code

``````1
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class Solution {
public:
int hammingWeight(uint32_t n) {
int sum = 0;
while (n != 0) {
sum++;
n &= (n - 1);
}
return sum;
}
};
``````