Commented the algorithm logic

greedy_algorithms/knapsack.cpp

@@ -1,12 +1,13 @@
 #include <iostream>
 using namespace std;
 
-struct Item {
+struct Item { 
     int weight;
     int profit;
 };
 
-float profitPerUnit(Item x) { return (float)x.profit / (float)x.weight; }
+//function to calculate input data for algo which is profit/wt of each item 
+float profitPerUnit(Item x) { return (float)x.profit / (float)x.weight; } 
 
 int partition(Item arr[], int low, int high) {
     Item pivot = arr[high];  // pivot
@@ -39,32 +40,38 @@ void quickSort(Item arr[], int low, int high) {
 
 int main() {
     cout << "\nEnter the capacity of the knapsack : ";
-    float capacity;
+    float capacity; //constraint 
     cin >> capacity;
     cout << "\n Enter the number of Items : ";
     int n;
     cin >> n;
+    //create item data structure, array here of size n
     Item *itemArray = new Item[n];
     for (int i = 0; i < n; i++) {
         cout << "\nEnter the weight and profit of item " << i + 1 << " : ";
         cin >> itemArray[i].weight;
         cin >> itemArray[i].profit;
     }
 
-    quickSort(itemArray, 0, n - 1);
+    quickSort(itemArray, 0, n - 1); // sorts by profitperunit parameter in the partition function
 
     // show(itemArray, n);
-
+    //Apply algorithm ->
     float maxProfit = 0;
     int i = n;
     while (capacity > 0 && --i >= 0) {
+        //start from item with largest profitperunit
         if (capacity >= itemArray[i].weight) {
+            //Add to the profit and reduce the capacity
             maxProfit += itemArray[i].profit;
             capacity -= itemArray[i].weight;
+            //Print the respective wt taken and profit of that item
             cout << "\n\t" << itemArray[i].weight << "\t"
                  << itemArray[i].profit;
         } else {
+            // take the fraction of item wt such that capacity is exhausted but not overloaded
             maxProfit += profitPerUnit(itemArray[i]) * capacity;
+            //print the fractional wt taken and profit obtained on this wt of item
             cout << "\n\t" << capacity << "\t"
                  << profitPerUnit(itemArray[i]) * capacity;
             capacity = 0;