added operator() overloading

lectures/23_priority_queues/video_test.cpp

@@ -0,0 +1,59 @@
+#include <iostream>
+#include <queue>
+#include <vector>
+
+class Video {
+public:
+    std::string title;
+    int viewCount;
+
+    Video(std::string t, int v) : title(t), viewCount(v) {}
+};
+
+// Comparator for sorting by viewCount (descending)
+// If Compare(a, b) returns true, it means a has a lower priority than b.
+// Thus here, this comparator function means a has a lower priority if it has a lower viewCount.
+// Therefore, the video with the highest viewCount stays on top of the heap, meaning this is a max heap.
+struct CompareByViews {
+    bool operator()(const Video& a, const Video& b) {
+        return a.viewCount < b.viewCount;
+    }
+};
+
+// Comparator for sorting by title (alphabetical order)
+// If Compare(a, b) returns true, it means a has lower priority than b.
+// Thus here, this comparator function means a has a lower priority if a's title goes after b's title.
+// Therefore, this is a min heap.
+struct CompareByTitle {
+    bool operator()(const Video& a, const Video& b) {
+        return a.title > b.title;  // Min-heap (A-Z)
+    }
+};
+
+int main() {
+    std::priority_queue<Video, std::vector<Video>, CompareByViews> pq_views;
+    std::priority_queue<Video, std::vector<Video>, CompareByTitle> pq_titles;
+
+    pq_views.push(Video("Video A", 500));
+    pq_views.push(Video("Video B", 1000));
+    pq_views.push(Video("Video C", 300));
+
+    pq_titles.push(Video("Video A", 500));
+    pq_titles.push(Video("Video B", 1000));
+    pq_titles.push(Video("Video C", 300));
+
+    std::cout << "Sorted by views:\n";
+    while (!pq_views.empty()) {
+        std::cout << pq_views.top().title << " (" << pq_views.top().viewCount << " views)\n";
+        pq_views.pop();
+    }
+
+    std::cout << "\nSorted by title:\n";
+    while (!pq_titles.empty()) {
+        std::cout << pq_titles.top().title << "\n";
+        pq_titles.pop();
+    }
+
+    return 0;
+}
+