Create minimum-number-of-people-to-teach.cpp

Author: kamyu104

C++/minimum-number-of-people-to-teach.cpp

@@ -0,0 +1,40 @@
+// Time:  O(n * m^2)
+// Space: O(n * m)
+
+class Solution {
+public:
+    int minimumTeachings(int n, vector<vector<int>>& languages, vector<vector<int>>& friendships) {
+        vector<unordered_set<int>> language_sets;
+        for (const auto& language : languages) {
+            language_sets.emplace_back(cbegin(language), cend(language));
+        }
+        unordered_set<int> candidates;
+        for (const auto& f : friendships) {
+            if (empty(intersect(language_sets[f[0] - 1], language_sets[f[1] - 1]))) {
+                candidates.emplace(f[0] - 1);
+                candidates.emplace(f[1] - 1);
+            }
+        }
+        vector<int> count(n);
+        for (const auto& i : candidates) {
+            for (const auto& l : language_sets[i]) {
+                ++count[l - 1];
+            }
+        }
+        return size(candidates) - *max_element(cbegin(count), cend(count));
+    }
+
+private:
+    unordered_set<int> intersect(const unordered_set<int>& a, const unordered_set<int>& b) {
+        if (size(a) > size(b)) {
+            return intersect(b, a);
+        }
+        unordered_set<int> result;
+        for (const auto& x : a) {
+            if (b.count(x)) {
+                result.emplace(x);
+            }
+        }
+        return result;
+    }
+};