You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
60 lines
1.8 KiB
60 lines
1.8 KiB
/**
|
|
* File: fractional_knapsack.java
|
|
* Created Time: 2023-07-20
|
|
* Author: krahets (krahets@163.com)
|
|
*/
|
|
|
|
package chapter_greedy;
|
|
|
|
import java.util.Arrays;
|
|
import java.util.Comparator;
|
|
|
|
/* Item */
|
|
class Item {
|
|
int w; // Item weight
|
|
int v; // Item value
|
|
|
|
public Item(int w, int v) {
|
|
this.w = w;
|
|
this.v = v;
|
|
}
|
|
}
|
|
|
|
public class fractional_knapsack {
|
|
/* Fractional knapsack: Greedy */
|
|
static double fractionalKnapsack(int[] wgt, int[] val, int cap) {
|
|
// Create an item list, containing two properties: weight, value
|
|
Item[] items = new Item[wgt.length];
|
|
for (int i = 0; i < wgt.length; i++) {
|
|
items[i] = new Item(wgt[i], val[i]);
|
|
}
|
|
// Sort by unit value item.v / item.w from high to low
|
|
Arrays.sort(items, Comparator.comparingDouble(item -> -((double) item.v / item.w)));
|
|
// Loop for greedy selection
|
|
double res = 0;
|
|
for (Item item : items) {
|
|
if (item.w <= cap) {
|
|
// If the remaining capacity is sufficient, put the entire item into the knapsack
|
|
res += item.v;
|
|
cap -= item.w;
|
|
} else {
|
|
// If the remaining capacity is insufficient, put part of the item into the knapsack
|
|
res += (double) item.v / item.w * cap;
|
|
// No remaining capacity left, thus break the loop
|
|
break;
|
|
}
|
|
}
|
|
return res;
|
|
}
|
|
|
|
public static void main(String[] args) {
|
|
int[] wgt = { 10, 20, 30, 40, 50 };
|
|
int[] val = { 50, 120, 150, 210, 240 };
|
|
int cap = 50;
|
|
|
|
// Greedy algorithm
|
|
double res = fractionalKnapsack(wgt, val, cap);
|
|
System.out.println("The maximum value within the bag capacity is " + res);
|
|
}
|
|
}
|