# 191. Number of 1 Bits(Solution || Leetcode easy || Java)

2 min readDec 20, 2022

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:

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

Example 2:

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

Example 3:

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

Constraints:

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

Follow up: If this function is called many times, how would you optimize it?

# SOLUTION:

`public class Solution {    // you need to treat n as an unsigned value    public int hammingWeight(int n) {        //start a counter to count number of 1 bits        int count = 0;        //as the input is of length 32 so, run the loop 32 times        for(int i = 0; i < 32; i++){            int k = n & 1;        //if the last bit is equal to 1 increase the counter            if(k == 1){                count++;            }        //as we have checked last bit so, right shift n            n = n >> 1;        }        return count;    }}`

Runtime1 ms

Beats

77.82%

Memory41.1 MB

Beats

50.58%

Thank you for reading. If you have any queries then, please let me know in the comment section. I will surely be responsive toward it.

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