[ready-oun] Week 03 solutions

number-of-1-bits/ready-oun.java

@@ -0,0 +1,31 @@
+class Solution {
+    public int hammingWeight(int n) {
+        int count = 0; 
+
+        while (n != 0) {
+            if ((n & 1) == 1) {
+                count++; 
+            }
+            n = n >>> 1;
+        }
+
+        return count; 
+    }
+}
+
+/**
+Time: O(1) – max 32 iterations (fixed bit size)
+Space: O(1)
+
+How it works: Shift each bit → Check → Count → Shift again
+    1. Shift each bit of n to the right
+    2. Check if the last bit is 1 using n & 1
+    3. If it is, increment the count
+    4. Shift n to the right using n = n >>> 1
+
+Learned:
+    (n & 1) isolates the least significant bit (LSB) to check if it’s 1
+    >>  : Arithmetic shift (fills in sign bit, so infinite loop for negatives)
+    >>> : Logical shift (always fills with 0, safe for negatives)
+    Java evaluates == before &, so use parentheses to control the order
+ */