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-rw-r--r--01-knapsack/Solver.java91
1 files changed, 91 insertions, 0 deletions
diff --git a/01-knapsack/Solver.java b/01-knapsack/Solver.java
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+++ b/01-knapsack/Solver.java
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+import java.io.*;
+import java.util.List;
+import java.util.ArrayList;
+
+/**
+ * The class <code>Solver</code> is an implementation of a greedy algorithm to solve the knapsack problem.
+ *
+ */
+public class Solver {
+
+ /**
+ * The main class
+ */
+ public static void main(String[] args) {
+ try {
+ solve(args);
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+ }
+
+ /**
+ * Read the instance, solve it, and print the solution in the standard output
+ */
+ public static void solve(String[] args) throws IOException {
+ String fileName = null;
+
+ // get the temp file name
+ for(String arg : args){
+ if(arg.startsWith("-file=")){
+ fileName = arg.substring(6);
+ }
+ }
+ if(fileName == null)
+ return;
+
+ // read the lines out of the file
+ List<String> lines = new ArrayList<String>();
+
+ BufferedReader input = new BufferedReader(new FileReader(fileName));
+ try {
+ String line = null;
+ while (( line = input.readLine()) != null){
+ lines.add(line);
+ }
+ }
+ finally {
+ input.close();
+ }
+
+
+ // parse the data in the file
+ String[] firstLine = lines.get(0).split("\\s+");
+ int items = Integer.parseInt(firstLine[0]);
+ int capacity = Integer.parseInt(firstLine[1]);
+
+ int[] values = new int[items];
+ int[] weights = new int[items];
+
+ for(int i=1; i < items+1; i++){
+ String line = lines.get(i);
+ String[] parts = line.split("\\s+");
+
+ values[i-1] = Integer.parseInt(parts[0]);
+ weights[i-1] = Integer.parseInt(parts[1]);
+ }
+
+ // a trivial greedy algorithm for filling the knapsack
+ // it takes items in-order until the knapsack is full
+ int value = 0;
+ int weight = 0;
+ int[] taken = new int[items];
+
+ for(int i=0; i < items; i++){
+ if(weight + weights[i] <= capacity){
+ taken[i] = 1;
+ value += values[i];
+ weight += weights[i];
+ } else {
+ taken[i] = 0;
+ }
+ }
+
+ // prepare the solution in the specified output format
+ System.out.println(value+" 0");
+ for(int i=0; i < items; i++){
+ System.out.print(taken[i]+" ");
+ }
+ System.out.println("");
+ }
+} \ No newline at end of file