From 02fb9fbb475b9170feec3b7a784801139915b721 Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Wed, 1 Oct 2025 13:26:17 +0300
Subject: [PATCH 1/6] Remove HW2-PersonalPage folder

---
 HW2-PersonalPage/_config.yml |  3 ---
 HW2-PersonalPage/index.md    | 10 ----------
 2 files changed, 13 deletions(-)
 delete mode 100644 HW2-PersonalPage/_config.yml
 delete mode 100644 HW2-PersonalPage/index.md

diff --git a/HW2-PersonalPage/_config.yml b/HW2-PersonalPage/_config.yml
deleted file mode 100644
index 418485a..0000000
--- a/HW2-PersonalPage/_config.yml
+++ /dev/null
@@ -1,3 +0,0 @@
-title: Grezin Danil
-description: Personal page of Danil Grezin hosted via GitHub
-theme: jekyll-theme-hacker
diff --git a/HW2-PersonalPage/index.md b/HW2-PersonalPage/index.md
deleted file mode 100644
index e1c0c7c..0000000
--- a/HW2-PersonalPage/index.md
+++ /dev/null
@@ -1,10 +0,0 @@
----
-layout: default
----
-
-# Education
-- Bachelor's degree student at St. Petersburg State University in the field of Programming Technology
-
-# Contacts
-- email: grezindanil@gmail.com
-- telegram: @dane4ka0_0

From 1b459cdec9b0ebe47ae4838b429cd2f26bd3a384 Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Sun, 12 Oct 2025 20:54:29 +0300
Subject: [PATCH 2/6] Add brute-force algorithm to count valid queens positions
 in chess

---
 HW4/chessQueenPosition/src/brute_force.py | 34 +++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 HW4/chessQueenPosition/src/brute_force.py

diff --git a/HW4/chessQueenPosition/src/brute_force.py b/HW4/chessQueenPosition/src/brute_force.py
new file mode 100644
index 0000000..678565d
--- /dev/null
+++ b/HW4/chessQueenPosition/src/brute_force.py
@@ -0,0 +1,34 @@
+import itertools
+
+
+def check_diagonal_attacks(queen_positions):
+    for i in range(len(queen_positions) - 1):
+        for j in range(i + 1, len(queen_positions)):
+            # Diagonal attack occurs when |row1 - row2| == |col1 - col2|
+            if abs(queen_positions[i][0] - queen_positions[j][0]) == abs(queen_positions[i][1] - queen_positions[j][1]):
+                return False
+    return True
+
+
+def brute_force_n_queens(n):
+    solutions_count = 0
+    # Generate all collumn non-repeating permutations (queens will be in different rows anyway)
+    all_col_permutations = itertools.permutations(range(n))
+
+    for col_positions in all_col_permutations:
+        # Assign rows to each column and put results in the list
+        queen_positions = list(enumerate(col_positions))
+        if check_diagonal_attacks(queen_positions):
+            solutions_count += 1
+
+    return solutions_count
+
+
+def main():
+    BOARD_SIZE = 8
+    print("result:")
+    print(brute_force_n_queens(BOARD_SIZE))
+
+
+if __name__ == "__main__":
+    main()

From 290b3260f153f241d8135f9ed1a8f84856daaf8c Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Sun, 12 Oct 2025 20:54:58 +0300
Subject: [PATCH 3/6] Add recursive algorithm to count valid queens positions
 in chess

---
 HW4/chessQueenPosition/src/recursive.py | 44 +++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 HW4/chessQueenPosition/src/recursive.py

diff --git a/HW4/chessQueenPosition/src/recursive.py b/HW4/chessQueenPosition/src/recursive.py
new file mode 100644
index 0000000..0fde684
--- /dev/null
+++ b/HW4/chessQueenPosition/src/recursive.py
@@ -0,0 +1,44 @@
+def is_pos_safe(queen_positions, new_pos):
+    for q_pos in queen_positions:
+        # Diagonal attack occurs when |row1 - row2| == |col1 - col2|
+        if abs(q_pos[0] - new_pos[0]) == abs(q_pos[1] - new_pos[1]):
+            return False
+    return True
+
+
+def recursive_n_queens(n, row=0, queen_positions=None, used_cols=None):
+    if queen_positions is None:
+        queen_positions = []
+    if used_cols is None:
+        used_cols = set()
+
+    if row == n:
+        return 1
+
+    solutions_count = 0
+
+    for col in range(n):
+        if col in used_cols:
+            continue
+
+        if is_pos_safe(queen_positions, [row, col]):
+            queen_positions.append([row, col])
+            used_cols.add(col)
+
+            solutions_count += recursive_n_queens(n, row + 1, queen_positions, used_cols)
+
+            # Backtrack
+            queen_positions.pop()
+            used_cols.remove(col)
+
+    return solutions_count
+
+
+def main():
+    BOARD_SIZE = 8
+    print("result:")
+    print(recursive_n_queens(BOARD_SIZE))
+
+
+if __name__ == "__main__":
+    main()

From e3c837cb09ca7e83daac32a7ee5ad8ce1ac9e60c Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Sun, 12 Oct 2025 20:55:13 +0300
Subject: [PATCH 4/6] Add bitwise algorithm to count valid queens positions in
 chess

---
 HW4/chessQueenPosition/src/bitwise.py | 36 +++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 HW4/chessQueenPosition/src/bitwise.py

diff --git a/HW4/chessQueenPosition/src/bitwise.py b/HW4/chessQueenPosition/src/bitwise.py
new file mode 100644
index 0000000..52a691b
--- /dev/null
+++ b/HW4/chessQueenPosition/src/bitwise.py
@@ -0,0 +1,36 @@
+def bitwise_n_queens(n):
+    bitmask = (1 << n) - 1
+
+    def count_solutions(row=0, cols=0, ascending_diag=0, descending_diag=0):
+        if row == n:
+            return 1
+
+        solutions_count = 0
+
+        all_attacks = cols | ascending_diag | descending_diag
+        available_positions = ~all_attacks & bitmask  # 1 = available
+
+        while available_positions:
+            col_bit = available_positions & -available_positions  # Rightmost available position
+            available_positions ^= col_bit
+
+            solutions_count += count_solutions(
+                row + 1,
+                cols | col_bit,
+                (ascending_diag | col_bit) << 1,  # Diagonals shift as we move down
+                (descending_diag | col_bit) >> 1,
+            )
+
+        return solutions_count
+
+    return count_solutions()
+
+
+def main():
+    BOARD_SIZE = 8
+    print("result:")
+    print(bitwise_n_queens(BOARD_SIZE))
+
+
+if __name__ == "__main__":
+    main()

From 435e25e291f70ab6054593c2dac51a65845264c6 Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Sun, 12 Oct 2025 20:55:33 +0300
Subject: [PATCH 5/6] Add complexity analysis for each algorithm

---
 HW4/chessQueenPosition/src/complexity.md | 26 ++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 HW4/chessQueenPosition/src/complexity.md

diff --git a/HW4/chessQueenPosition/src/complexity.md b/HW4/chessQueenPosition/src/complexity.md
new file mode 100644
index 0000000..42d1f54
--- /dev/null
+++ b/HW4/chessQueenPosition/src/complexity.md
@@ -0,0 +1,26 @@
+# Оценка сложности / Complexity analysis
+
+## 1. Переборное решение / Brute-force solution
+
+Сложность: O(N! * N^2)
+Обоснование: N! перестановок * O(N^2) проверка корректности всех пар ферзей (N(N-1)/2 сравнений)
+
+Complexity: O(N! * N^2)
+Explanation: N! permutations * O(N^2) validity check of all queen pairs (N(N-1)/2 comparisons)
+
+## 2. Рекурсивное решение / Recursive solution
+
+Сложность: O(N! * N)
+Обоснование: N! расстановок * O(N) проверка корректности для каждого нового ферзя
+
+Complexity: O(N! * N)
+Explanation: N! configurations * O(N) validity check for each new queen
+
+## 3. Побитовое решение / Bitwise solution
+
+Сложность: O(N!)
+Обоснование: N! расстановок * O(1) битовые операции
+
+Complexity: O(N!)
+Explanation: N! configurations * O(1) bitwise operations
+

From b750cd55aee48850bbe6b99e46123289eb58145f Mon Sep 17 00:00:00 2001
From: Dan <grezindanil@gmail.com>
Date: Sun, 12 Oct 2025 21:08:08 +0300
Subject: [PATCH 6/6] Add final newline

---
 HW4/chessQueenPosition/src/bitwise.py     | 1 +
 HW4/chessQueenPosition/src/brute_force.py | 1 +
 HW4/chessQueenPosition/src/recursive.py   | 1 +
 3 files changed, 3 insertions(+)

diff --git a/HW4/chessQueenPosition/src/bitwise.py b/HW4/chessQueenPosition/src/bitwise.py
index 52a691b..f252670 100644
--- a/HW4/chessQueenPosition/src/bitwise.py
+++ b/HW4/chessQueenPosition/src/bitwise.py
@@ -34,3 +34,4 @@ def main():
 
 if __name__ == "__main__":
     main()
+
diff --git a/HW4/chessQueenPosition/src/brute_force.py b/HW4/chessQueenPosition/src/brute_force.py
index 678565d..5d6e08c 100644
--- a/HW4/chessQueenPosition/src/brute_force.py
+++ b/HW4/chessQueenPosition/src/brute_force.py
@@ -32,3 +32,4 @@ def main():
 
 if __name__ == "__main__":
     main()
+
diff --git a/HW4/chessQueenPosition/src/recursive.py b/HW4/chessQueenPosition/src/recursive.py
index 0fde684..d42cca9 100644
--- a/HW4/chessQueenPosition/src/recursive.py
+++ b/HW4/chessQueenPosition/src/recursive.py
@@ -42,3 +42,4 @@ def main():
 
 if __name__ == "__main__":
     main()
+