Create queens-that-can-attack-the-king.cpp

Author: kamyu104

C++/queens-that-can-attack-the-king.cpp

@@ -0,0 +1,38 @@
+// Time:  O(1)
+// Space: O(1)
+
+class Solution {
+private:
+    template <typename T>
+    struct PairHash {
+        size_t operator()(const pair<T, T>& p) const {
+            size_t seed = 0;
+            seed ^= std::hash<T>{}(p.first)  + 0x9e3779b9 + (seed<<6) + (seed>>2);
+            seed ^= std::hash<T>{}(p.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
+            return seed;
+        }
+    };
+
+public:
+    vector<vector<int>> queensAttacktheKing(vector<vector<int>>& queens, vector<int>& king) {
+        static const vector<pair<int, int>> directions =
+          {{-1, 0}, {0, 1}, {1, 0}, {0, -1},
+           {-1, 1}, {1, 1}, {1, -1}, {-1, -1}};
+        vector<vector<int>> result;
+        unordered_set<pair<int, int>, PairHash<int>> lookup;
+        for (const auto& queen : queens) {
+            lookup.emplace(queen[0], queen[1]);
+        }
+        for (const auto& [dx, dy] : directions) {
+            for (int i = 1; i <= 7; ++i) {
+                int x = king[0] + dx * i;
+                int y = king[1] + dy * i;
+                if (lookup.count(make_pair(x, y))) {
+                    result.push_back({x, y});
+                    break;
+                }
+            }
+        }
+        return result;
+    }
+};