Create fractional-knapsack.cpp

GreedyAlgorithm/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; 
+}