Add step4

Author: colorbox

347/step4.cpp

@@ -0,0 +1,37 @@
+/*
+priority_queueの最大サイズを制限する
+*/
+class Solution {
+ public:
+  vector<int> topKFrequent(vector<int>& nums, int k) {
+    map<int, int> num_to_count;
+    for (int num: nums) {
+      num_to_count[num]++;
+    }
+
+    priority_queue<NumCount, vector<NumCount>, greater<NumCount>> num_count;
+    for (auto [num, count] : num_to_count) {
+      num_count.push({num, count});
+      if (num_count.size() > k) {
+        num_count.pop();
+      }
+    }
+
+    vector<int> answer;
+    for (int i = 0; i < k; i++) {
+      answer.push_back(num_count.top().num);
+      num_count.pop();
+    }
+    return answer;
+  }
+
+ private:
+  struct NumCount {
+    int num;
+    int count;
+
+    bool operator> (const NumCount& other) const {
+      return count > other.count;
+    }
+  };
+};