Create Fractional_knapsack.cpp

Author: pradhuman131

DP/Knapsack/Fractional_knapsack.cpp

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+
+// C/C++ program to solve fractional Knapsack Problem 
+#include <bits/stdc++.h> 
+  
+using namespace std; 
+  
+// Structure for an item which stores weight and corresponding 
+// value of Item 
+struct Item 
+{ 
+    int value, weight; 
+  
+    // Constructor 
+    Item(int value, int weight) : value(value), weight(weight) 
+    {} 
+}; 
+  
+// Comparison function to sort Item according to val/weight ratio 
+bool cmp(struct Item a, struct Item b) 
+{ 
+    double r1 = (double)a.value / a.weight; 
+    double r2 = (double)b.value / b.weight; 
+    return r1 > r2; 
+} 
+  
+// Main greedy function to solve problem 
+double fractionalKnapsack(int W, struct Item arr[], int n) 
+{ 
+    //    sorting Item on basis of ratio 
+    sort(arr, arr + n, cmp); 
+  
+    //    Uncomment to see new order of Items with their ratio 
+    /* 
+    for (int i = 0; i < n; i++) 
+    { 
+        cout << arr[i].value << "  " << arr[i].weight << " : " 
+             << ((double)arr[i].value / arr[i].weight) << endl; 
+    } 
+    */
+  
+    int curWeight = 0;  // Current weight in knapsack 
+    double finalvalue = 0.0; // Result (value in Knapsack) 
+  
+    // Looping through all Items 
+    for (int i = 0; i < n; i++) 
+    { 
+        // If adding Item won't overflow, add it completely 
+        if (curWeight + arr[i].weight <= W) 
+        { 
+            curWeight += arr[i].weight; 
+            finalvalue += arr[i].value; 
+        } 
+  
+        // If we can't add current Item, add fractional part of it 
+        else
+        { 
+            int remain = W - curWeight; 
+            finalvalue += arr[i].value * ((double) remain / arr[i].weight); 
+            break; 
+        } 
+    } 
+  
+    // Returning final value 
+    return finalvalue; 
+} 
+  
+// driver program to test above function 
+int main() 
+{ 
+    int W = 50;   //    Weight of knapsack 
+    Item arr[] = {{60, 10}, {100, 20}, {120, 30}}; 
+  
+    int n = sizeof(arr) / sizeof(arr[0]); 
+  
+    cout << "Maximum value we can obtain = "
+         << fractionalKnapsack(W, arr, n); 
+    return 0; 
+}