1 files changed, 42 insertions, 0 deletions

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";
+}