Create sort-features-by-popularity.cpp

Author: kamyu104

C++/sort-features-by-popularity.cpp

@@ -0,0 +1,41 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<string> sortFeatures(vector<string>& features, vector<string>& responses) {
+        unordered_set<string> features_set(cbegin(features), cend(features));
+        unordered_map<string, int> order;
+        for (int i = 0; i < size(features); ++i) {
+            order[features[i]] = i;
+        }
+        unordered_map<string, int> freq;
+        for (const auto&r : responses) {
+            const auto& words = split(r, ' ');
+            unordered_set<string> words_set(cbegin(words), cend(words));
+            for (const auto& word : words_set) {
+                if (features_set.count(word)) {
+                    ++freq[word];
+                }
+            }
+        }
+        sort(begin(features), end(features),
+             [&freq, &order](const auto& a, const auto& b) {
+                 return pair(-freq[a], order[a]) < pair(-freq[b], order[b]);
+             });
+        return features;
+    }
+
+private:
+    vector<string> split(const string& s, const char delim) {
+        vector<string> tokens;
+        stringstream ss(s);
+        string token;
+        while (getline(ss, token, delim)) {
+            if (!empty(token)) {
+                tokens.emplace_back(token);
+            }
+        }
+        return tokens;
+    }
+};