Create 1792. Maximum Average Pass Ratio (#662)

Author: Chayandas07

1792. Maximum Average Pass Ratio

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+class Solution {
+public:
+    double maxAverageRatio(vector<vector<int>>& classes, int extraStudents) {
+        int classesLen = classes.size();
+        
+        // pq to know which class will increase the avg the most
+        priority_queue<pair<double, int>> valueQueue;
+        double finalAvg = 0;
+        double localAvg = 0;
+
+
+        // going through all classes adding them to finalAvg and
+        // placing their avg increase into the pq if we were to add
+        // an extra student there
+        for (int i = 0; i < classesLen; ++i) {
+            localAvg = static_cast<double>(classes[i][0]) / classes[i][1];
+            valueQueue.push({(static_cast<double>(classes[i][0] + 1) / (classes[i][1] + 1)) - localAvg, i});
+            finalAvg += localAvg;
+        }
+
+        // devide the avg once after the loop
+        finalAvg /= classesLen;
+
+
+        // while there are students to distribute we go through the pq
+        while (extraStudents > 0) {
+            // we take the class with highest avg inc value
+            auto top = valueQueue.top();
+            valueQueue.pop();
+
+            // add the value / classLen to the finalAvg
+            finalAvg += top.first / classesLen;
+
+            // we add a student to that class
+            ++classes[top.second][1];
+            ++classes[top.second][0];
+
+            // recalculate that class avg inc if we were to add an
+            // extra student
+            localAvg = static_cast<double>(classes[top.second][0]) / classes[top.second][1];
+            valueQueue.push({(static_cast<double>(classes[top.second][0] + 1) / (classes[top.second][1] + 1)) - localAvg, top.second});
+            
+            // decrement the extraStudents left
+            --extraStudents;
+        }
+
+        return finalAvg;
+    }
+};