diff --git a/0191.Number-of-1-Bits/memo.md b/0191.Number-of-1-Bits/memo.md
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+# 191. Number of 1 Bits
+
+## step1
+1mもかからなかった。strでも書く。
+
+## 他の人のコード
+https://github.com/Ryotaro25/leetcode_first60/pull/76
+
+> 整数の割り算は遅い、ビット演算は速い、という感覚は持っておいたほうが良いと思います
+pythonだと差はなさそう
+
+> 分割統治法による解法もあります。
+
+この解法はおもしろい。有名な解法らしい。
+
+足している数字はそれぞれ二進数で0101..., 00110011...,00001111...となっている。
+
+一行目で2bitずつ区切った場所のbitカウントを2bitずつ2進数で表現し、二行目で4bit,..最終的に32bitのbitカウントになる。
+
+> https://en.wikipedia.org/wiki/Hamming_weight#Efficient_implementation
+
+1. 上の解法はtree patternと呼ばれている。
+> For processors lacking those features, the best solutions known are based on adding counts in a tree pattern
+> The above implementations have the best worst-case behavior of any known algorithm
+
+2. 上の亜種がある。0x01010101をかける。筆算を考えるとわかりやすい。
+
+以下でもいけるのではと思ったが、よく考えるとうまくいかない。4bitで、最大値を表現できないため
+
+```python
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        n = n & 0xffffffff
+        n = (n & 0x55555555) + ((n >> 1) & 0x55555555)
+        n = (n & 0x33333333) + ((n >> 2) & 0x33333333)
+        return ((n * 0x11111111) & 0xffffffff) >> 28
+```
+
+3. &を取ると右端の1が消える。これも実装してみる。
+> As Wegner described in 1960,[14] the bitwise AND of x with x − 1 differs from x only in zeroing out the least significant nonzero bit: subtracting 1 changes the rightmost string of 0s to 1s, and changes the rightmost 1 to a 0. If x originally had n bits that were 1, then after only n iterations of this operation, x will be reduced to zero. The following implementation is based on this principle.
+
+4. 大きなメモリを使う解法
+
+
+---
+
+そもそも、builtinに専用の関数がある
+https://docs.python.org/ja/3/library/stdtypes.html#int.bit_count
+
+
+
+> https://github.com/rihib/leetcode/pull/46#pullrequestreview-2381278969
+
+勉強になる。特に以下。
+> ここで注目したいのは、 xとその２の補数はお互いにRightmost set bit以外が反転しているということである。つまり、x & -xとすると、Rightmost set bitのみが1になったビット列を得ることができる。よって、x - (x & -x)としてあげれば、 xのRightmost set bitをunsetすることができるのである。
+
+> Rightmost unset bitをsetする方法
+flippedで考えて最後にflippする
+
+https://www.geeksforgeeks.org/dsa/set-rightmost-unset-bit/
+
diff --git a/0191.Number-of-1-Bits/step1.py b/0191.Number-of-1-Bits/step1.py
new file mode 100644
index 0000000..cbcfa27
--- /dev/null
+++ b/0191.Number-of-1-Bits/step1.py
@@ -0,0 +1,8 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        hamming_weight = 0
+        while n > 0:
+            hamming_weight += n & 1
+            n >>= 1
+        return hamming_weight
+
diff --git a/0191.Number-of-1-Bits/step1_str.py b/0191.Number-of-1-Bits/step1_str.py
new file mode 100644
index 0000000..956912a
--- /dev/null
+++ b/0191.Number-of-1-Bits/step1_str.py
@@ -0,0 +1,4 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        return sum(int(bit) for bit in f"{n:b}")
+
diff --git a/0191.Number-of-1-Bits/step2_builtin.py b/0191.Number-of-1-Bits/step2_builtin.py
new file mode 100644
index 0000000..e2bcead
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+++ b/0191.Number-of-1-Bits/step2_builtin.py
@@ -0,0 +1,3 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        return n.bit_count()
diff --git a/0191.Number-of-1-Bits/step2_divide_and_conque_v2.py b/0191.Number-of-1-Bits/step2_divide_and_conque_v2.py
new file mode 100644
index 0000000..57f6813
--- /dev/null
+++ b/0191.Number-of-1-Bits/step2_divide_and_conque_v2.py
@@ -0,0 +1,7 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        n = (n & 0x55555555) + ((n >> 1) & 0x55555555)
+        n = (n & 0x33333333) + ((n >> 2) & 0x33333333)
+        n = (n + (n >> 4)) & 0x0f0f0f0f
+
+        return (n * 0x01010101) >> 24
diff --git a/0191.Number-of-1-Bits/step2_divide_and_conquer.py b/0191.Number-of-1-Bits/step2_divide_and_conquer.py
new file mode 100644
index 0000000..b459c5b
--- /dev/null
+++ b/0191.Number-of-1-Bits/step2_divide_and_conquer.py
@@ -0,0 +1,9 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        n = n & 0xffffffff
+        n = (n & 0x55555555) + ((n >> 1) & 0x55555555)
+        n = (n & 0x33333333) + ((n >> 2) & 0x33333333)
+        n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f)
+        n = (n & 0x00ff00ff) + ((n >> 8) & 0x00ff00ff)
+        n = (n & 0x0000ffff) + ((n >> 16) & 0x0000ffff)
+        return n
\ No newline at end of file
diff --git a/0191.Number-of-1-Bits/step2_lookup.py b/0191.Number-of-1-Bits/step2_lookup.py
new file mode 100644
index 0000000..646f336
--- /dev/null
+++ b/0191.Number-of-1-Bits/step2_lookup.py
@@ -0,0 +1,15 @@
+class Solution:
+    WORDBITS = [0] * 65536
+
+    @classmethod
+    def init_wordbits(cls):
+        for i in range(1, len(cls.WORDBITS)):
+            cls.WORDBITS[i] = cls.WORDBITS[i >> 1] + (i & 1)
+
+    def __init__(self):
+        if self.WORDBITS[1] == 0:
+            self.init_wordbits()
+
+    def hammingWeight(self, n: int) -> int:
+        n = n & 0xffffffff
+        return self.WORDBITS[n & 0xffff] + self.WORDBITS[n >> 16]
\ No newline at end of file
diff --git a/0191.Number-of-1-Bits/step2_wegner.py b/0191.Number-of-1-Bits/step2_wegner.py
new file mode 100644
index 0000000..2845dec
--- /dev/null
+++ b/0191.Number-of-1-Bits/step2_wegner.py
@@ -0,0 +1,8 @@
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        hamming_weight = 0
+        while n > 0:
+            n &= n - 1
+            hamming_weight += 1
+        return hamming_weight
+