- 輪流來自中設置的最大,裝入一個新的集合S(第2項,價值18)
- 嘗試用價值發現的最大項目< =(20 - 18):無,加S到一組列表。
- 如果IN不爲空GOTO 1
迭代:
IN: 9, 18, 7, 8, 4, 9, 11, 15, 3, 8
S1 (18) : 2:18 IN: 9, _, 7, 8, 4, 9, 11, 15, 3, 8
S2 (19) : 8:15, 5:4 IN: 9, _, 7, 8, _, 9, 11, _, 3, 8
S3 (20) : 7:11, 1:9 IN: _, _, 7, 8, _, 9, _, _, 3, 8
S4 (20) : 6: 9, 4:8, 0:3 IN: _, _, 7, _, _, _, _, _, _, 8
S5 (15) : 10: 8, 3:7 IN: _, _, _, _, _, _, _, _, _, _
的代碼:
public class Knapsack {
public static void knapsack(int capacity, int[] values, List<int[]> indices) {
int[] in = Arrays.copyOf(values, values.length);
List<Integer> workspace = new LinkedList<>();
int wCapacity = capacity;
boolean inProgress = true;
while(inProgress) {
int greatestValue = -1;
int greatestIndex = -1;
for(int i = 0; i < in.length; ++i) {
int value = in[i];
if( value > Integer.MIN_VALUE
&& greatestValue < value && value <= wCapacity)
{
greatestValue = value;
greatestIndex = i;
}
}
if(greatestIndex >= 0) {
workspace.add(greatestIndex);
in[greatestIndex] = Integer.MIN_VALUE;
wCapacity -= greatestValue;
} else if(workspace.isEmpty()) {
inProgress = false;
} else {
int[] ws = new int[workspace.size()];
for(int i = 0; i < workspace.size(); ++i) {
ws[i] = workspace.get(i).intValue();
}
indices.add(ws);
workspace = new LinkedList<>();
wCapacity = capacity;
}
}
}
static void print(int[] values, List<int[]> indices)
{
int r = 0;
for(int[] t : indices) {
String items = "";
int sum = 0;
for(int index : t) {
int value = values[index];
if(! items.isEmpty()) {
items += ", ";
}
items += index + ":" + value;
sum += value;
}
System.out.println("S" + ++r + " (" + sum + ") : " + items);
}
}
public static void main(String[] args) {
int[] values = { 9, 18, 7, 8, 4, 9, 11, 15, 3, 8 };
List<int[]> indices = new LinkedList<>();
knapsack(20, values, indices);
print(values, indices);
}
}
其結果是:
S1 (18) : 1:18
S2 (19) : 7:15, 4:4
S3 (20) : 6:11, 0:9
S4 (20) : 5:9, 3:8, 8:3
S5 (15) : 9:8, 2:7
聽起來像揹包的一個變體:http://en.wikipedia.org/wi ki/Knapsack_problem – reprogrammer
這是一個揹包問題的變體 - 它被稱爲[** Bin Packing Problem **](http://en.wikipedia.org/wiki/Bin_packing_problem)。這是NP難,但有貪婪的近似計劃,在鏈接的維基文章中列出了一個。 – jedwards
鑑於問題是NP難題,您需要解決的最大問題有多大,您希望得到最佳解決方案嗎? – NPE