From 96254947699986c59f0dc63d69fd4b76bd3ed43e Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Mon, 6 Jul 2026 19:08:08 +0200
Subject: Initial commit

---
 .../chessboard_and_queens_1624.cpp                 | 42 ++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 01_introductory_problems/chessboard_and_queens_1624.cpp

(limited to '01_introductory_problems/chessboard_and_queens_1624.cpp')

diff --git a/01_introductory_problems/chessboard_and_queens_1624.cpp b/01_introductory_problems/chessboard_and_queens_1624.cpp
new file mode 100644
index 0000000..d595232
--- /dev/null
+++ b/01_introductory_problems/chessboard_and_queens_1624.cpp
@@ -0,0 +1,42 @@
+#include <bitset>
+#include <iostream>
+#include <string>
+
+void set_bit(std::bitset<64>& r, int i, int j) {
+	if (i >= 0 && i < 8 && j >= 0 && j < 8)
+		r |= 1ULL << (unsigned long long)(8*i + j);
+}
+
+std::bitset<64> maskall(const std::bitset<64>& b, int i, int j) {
+	std::bitset<64> r{b};
+	r |= 0x0101010101010101ULL << (unsigned long long)j;
+	for (int k = 0; k < 8; k++) {
+		set_bit(r, k, k+j-i);
+		set_bit(r, k, -k+j+i);
+	}
+	return r;
+}
+
+long long f(std::bitset<64>& b, int i) {
+	if (i == 8)
+		return 1;
+	long long s{0};
+	for (int j = 0; j < 8; j++) {
+		if (!b[8*i+j]) {
+			auto rr = maskall(b, i, j);
+			s += f(rr, i+1);
+		}
+	}
+	return s;
+}
+
+int main() {
+	std::bitset<64> b{0};
+	std::string s;
+	for (int i = 0; i < 8; i++) {
+		std::cin >> s;
+		for (int j = 0; j < 8; j++)
+			b[8*i+j] = s[j] == '*';
+	}
+	std::cout << f(b, 0) << "\n";
+}
-- 
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