New Problem Solution - "Minimum Number of People to Teach"

README.md

@@ -21,6 +21,7 @@ LeetCode
 |1750|[Minimum Length of String After Deleting Similar Ends](https://leetcode.com/problems/minimum-length-of-string-after-deleting-similar-ends/) | [C++](./algorithms/cpp/minimumLengthOfStringAfterDeletingSimilarEnds/MinimumLengthOfStringAfterDeletingSimilarEnds.cpp)|Medium|
 |1749|[Maximum Absolute Sum of Any Subarray](https://leetcode.com/problems/maximum-absolute-sum-of-any-subarray/) | [C++](./algorithms/cpp/maximumAbsoluteSumOfAnySubarray/MaximumAbsoluteSumOfAnySubarray.cpp)|Medium|
 |1748|[Sum of Unique Elements](https://leetcode.com/problems/sum-of-unique-elements/) | [C++](./algorithms/cpp/sumOfUniqueElements/SumOfUniqueElements.cpp)|Easy|
+|1733|[Minimum Number of People to Teach](https://leetcode.com/problems/minimum-number-of-people-to-teach/) | [C++](./algorithms/cpp/minimumNumberOfPeopleToTeach/MinimumNumberOfPeopleToTeach.cpp)|Medium|
 |1732|[Find the Highest Altitude](https://leetcode.com/problems/find-the-highest-altitude/) | [C++](./algorithms/cpp/findTheHighestAltitude/FindTheHighestAltitude.cpp)|Easy|
 |1605|[Find Valid Matrix Given Row and Column Sums](https://leetcode.com/problems/find-valid-matrix-given-row-and-column-sums/) | [C++](./algorithms/cpp/FindValidMatrixGivenRowAndColumnSums/FindValidMatrixGivenRowAndColumnSums.cpp)|Medium|
 |1573|[Number of Ways to Split a String](https://leetcode.com/problems/number-of-ways-to-split-a-string/) | [C++](./algorithms/cpp/NumberOfWaysToSplitString/NumberOfWaysToSplitString.cpp)|Medium|

algorithms/cpp/minimumNumberOfPeopleToTeach/MinimumNumberOfPeopleToTeach.cpp

@@ -0,0 +1,97 @@
+// Source : https://leetcode.com/problems/minimum-number-of-people-to-teach/
+// Author : Hao Chen
+// Date   : 2021-02-17
+
+/***************************************************************************************************** 
+ *
+ * On a social network consisting of m users and some friendships between users, two users can 
+ * communicate with each other if they know a common language.
+ * 
+ * You are given an integer n, an array languages, and an array friendships where:
+ * 
+ * 	There are n languages numbered 1 through n,
+ * 	languages[i] is the set of languages the i​​​​​​th​​​​ user knows, and
+ * 	friendships[i] = [u​​​​​​i​​​, v​​​​​​i] denotes a friendship between the users u​​​​​​​​​​​
+ * i​​​​​ and vi.
+ * 
+ * You can choose one language and teach it to some users so that all friends can communicate with 
+ * each other. Return the minimum number of users you need to teach.
+ * Note that friendships are not transitive, meaning if x is a friend of y and y is a friend of z, 
+ * this doesn't guarantee that x is a friend of z.
+ * 
+ * Example 1:
+ * 
+ * Input: n = 2, languages = [[1],[2],[1,2]], friendships = [[1,2],[1,3],[2,3]]
+ * Output: 1
+ * Explanation: You can either teach user 1 the second language or user 2 the first language.
+ * 
+ * Example 2:
+ * 
+ * Input: n = 3, languages = [[2],[1,3],[1,2],[3]], friendships = [[1,4],[1,2],[3,4],[2,3]]
+ * Output: 2
+ * Explanation: Teach the third language to users 1 and 3, yielding two users to teach.
+ * 
+ * Constraints:
+ * 
+ * 	2 <= n <= 500
+ * 	languages.length == m
+ * 	1 <= m <= 500
+ * 	1 <= languages[i].length <= n
+ * 	1 <= languages[i][j] <= n
+ * 	1 <= u​​​​​​i < v​​​​​​i <= languages.length
+ * 	1 <= friendships.length <= 500
+ * 	All tuples (u​​​​​i, v​​​​​​i) are unique
+ * 	languages[i] contains only unique values
+ ******************************************************************************************************/
+
+class Solution {
+
+public:
+    bool hasLang(vector<int>& langlist, int lang){
+        for(auto& l : langlist) {
+            if (l == lang) return true;
+        }
+        return false;
+    }
+    
+    bool canComm(int u, int v, int n, vector<vector<bool>>& langs) {
+        for (int l=0; l<n; l++) {
+            if (langs[u][l] && langs[v][l]) return true;
+        }
+        return false;
+    }
+    
+    int minimumTeachings(int n, vector<vector<int>>& languages, vector<vector<int>>& friendships) {
+        int persons = languages.size();
+        //use to check a person know a langauge or not
+        vector<vector<bool>> langs(persons, vector<bool>(n, false));
+        for (int p=0; p<persons; p++) {
+            for(int l=0; l<languages[p].size(); l++) {
+                langs[p][languages[p][l]-1] = true;
+            }
+        } 
+        
+        int result = persons;
+        vector<vector<bool>> langToTeach(n, vector<bool>(persons, false));
+        for (int l=0; l <n; l++) {
+            int cnt = 0;
+            vector<bool> teach(persons, false);
+            for (auto& fs : friendships) {
+                int u = fs[0] - 1;
+                int v = fs[1] - 1;
+
+                if (canComm(u, v, n, langs)) continue;
+
+                if (langs[u][l]==false && teach[u]==false) {
+                    teach[u] = true; cnt++;
+                }
+                if (langs[v][l]==false && teach[v]==false) {
+                    teach[v] = true; cnt++;
+                }
+            }
+            result = min(result, cnt);
+        }
+        
+        return result;
+    }
+};