cpp: try ‹2092. Find All People With Secret›

Signed-off-by: Matej Focko <mfocko@redhat.com>

cpp/find-all-people-with-secret.cpp

@@ -0,0 +1,97 @@
+#include <algorithm>
+#include <iterator>
+#include <set>
+#include <vector>
+
+class Solution {
+    void handle_previous_meeting(std::set<int> &overall,
+                                 std::set<int> &current) {
+        std::vector<int> intersection;
+        std::set_intersection(current.begin(), current.end(), overall.begin(),
+                              overall.end(), std::back_inserter(intersection));
+
+        if (!intersection.empty()) {
+            overall.insert(current.begin(), current.end());
+        }
+
+        current = {};
+    }
+
+  public:
+    std::vector<int> findAllPeople(int n,
+                                   std::vector<std::vector<int>> meetings,
+                                   int firstPerson) {
+        std::sort(meetings.begin(), meetings.end(),
+                  [](const auto &l, const auto &r) { return l[2] < r[2]; });
+
+        std::set<int> knowers{0, firstPerson};
+
+        std::set<int> current_meeting{};
+        int timestamp = -1;
+        for (const auto &meeting : meetings) {
+            auto a = meeting[0];
+            auto b = meeting[1];
+            auto t = meeting[2];
+
+            if (t != timestamp) {
+                // handle the previous meeting
+                handle_previous_meeting(knowers, current_meeting);
+                timestamp = t;
+            }
+
+            // just add the members and carry on
+            current_meeting.insert(a);
+            current_meeting.insert(b);
+        }
+        handle_previous_meeting(knowers, current_meeting);
+
+        return std::vector<int>(knowers.begin(), knowers.end());
+    }
+};
+
+#ifdef _MF_TEST
+#include <gtest/gtest.h>
+
+TEST(examples, no_1) {
+    Solution s;
+    EXPECT_EQ(
+        (s.findAllPeople(6,
+                         std::vector{std::vector{1, 2, 5}, std::vector{2, 3, 8},
+                                     std::vector{1, 5, 10}},
+                         1)),
+        (std::vector{0, 1, 2, 3, 5}));
+}
+TEST(examples, no_2) {
+    Solution s;
+    EXPECT_EQ(
+        (s.findAllPeople(4,
+                         std::vector{std::vector{3, 1, 3}, std::vector{1, 2, 2},
+                                     std::vector{0, 3, 3}},
+                         3)),
+        (std::vector{0, 1, 3}));
+}
+TEST(examples, no_3) {
+    Solution s;
+    EXPECT_EQ(
+        (s.findAllPeople(5,
+                         std::vector{std::vector{3, 4, 2}, std::vector{1, 2, 1},
+                                     std::vector{2, 3, 1}},
+                         1)),
+        (std::vector{0, 1, 2, 3, 4}));
+}
+
+TEST(wrong_answer, no_1) {
+    Solution s;
+    EXPECT_EQ(
+        (s.findAllPeople(6,
+                         std::vector{std::vector{0, 2, 1}, std::vector{1, 3, 1},
+                                     std::vector{4, 5, 1}},
+                         1)),
+        (std::vector{0, 1, 2, 3}));
+}
+
+int main(int argc, char **argv) {
+    testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}
+#endif