diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index ece688b..ebe03b5 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -184,4 +184,5 @@ mod p502_ipo;
 mod p373_find_k_pairs_with_smallest_sums;
 mod p295_find_median_from_data_stream;
 mod p67_add_binary;
-mod p190_reverse_bits;
\ No newline at end of file
+mod p190_reverse_bits;
+mod p191_number_of_1_bits;
\ No newline at end of file
diff --git a/src/problem/p191_number_of_1_bits.rs b/src/problem/p191_number_of_1_bits.rs
new file mode 100644
index 0000000..390e5a0
--- /dev/null
+++ b/src/problem/p191_number_of_1_bits.rs
@@ -0,0 +1,68 @@
+/**
+ * [191] Number of 1 Bits
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn hamming_weight(n: i32) -> i32 {
+        static ARRAY: [i32; 31] = [
+            1 << 30,
+            1 << 29,
+            1 << 28,
+            1 << 27,
+            1 << 26,
+            1 << 25,
+            1 << 24,
+            1 << 23,
+            1 << 22,
+            1 << 21,
+            1 << 20,
+            1 << 19,
+            1 << 18,
+            1 << 17,
+            1 << 16,
+            1 << 15,
+            1 << 14,
+            1 << 13,
+            1 << 12,
+            1 << 11,
+            1 << 10,
+            1 << 9,
+            1 << 8,
+            1 << 7,
+            1 << 6,
+            1 << 5,
+            1 << 4,
+            1 << 3,
+            1 << 2,
+            1 << 1,
+            1
+        ];
+        
+        let mut result = 0;
+        
+        for i in 0..31 {
+            if n & ARRAY[i] == ARRAY[i] {
+                result += 1;
+            }
+        }
+        
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_191() {
+        assert_eq!(3, Solution::hamming_weight(11));
+        assert_eq!(1, Solution::hamming_weight(128));
+    }
+}