Our Combination code in Java.
Combination Class File:
package miscellaneous;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Combination {
public List<String> words;
public int r; // min length of word
protected List<String[]> comb_store;
private int i;
public Combination() {
}
// point of entry
public List<String[]> possibleWordCombinations(List<String> candidates, int size) {
words = candidates;
r = size;
comb_store = new ArrayList<>();
i = 0;
// check for conformity
if (r <= 0 || r > words.size()) {
comb_store = new ArrayList<>();
} else if (r == 1) {
for (; i < words.size(); i++) {
comb_store.add(new String[]{words.get(i)});
}
} else {
progressiveCombination();
}
return comb_store;
}
// do combinations for all 'words' element
private void progressiveCombination() {
// single member list
repetitivePairing(Arrays.asList(words.get(i)), i + 1);
if (i + r <= words.size()) {
// move on to next degree
i++;
progressiveCombination();
}
}
// do all possible combinations for 1st element of this array
private void repetitivePairing(List<String> prefix, int position) {
List<String>[] auxiliary_store = new List[words.size() - position];
for (int j = 0; position < words.size(); position++, j++) {
// check if desired -- r -- size will be realised
if (r - prefix.size() <= words.size() - position) {
auxiliary_store[j] = new ArrayList<>();
auxiliary_store[j].addAll(prefix);
auxiliary_store[j].add(words.get(position));
if (auxiliary_store[j].size() < r) {
// see to adding next word on
repetitivePairing(auxiliary_store[j], position + 1);
} else {
comb_store.add(auxiliary_store[j].toArray(new String[0]));
}
}
}
}
}Main Class:
package miscellaneous;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Miscellaneous {
public static void main(String[] args) {
List<String> goods = new ArrayList<>();
goods.add("Eno");
goods.add("Chidi");
goods.add("Olu");
goods.add("Ahmed");
goods.add("Osas");
goods.add("Gbeda");
Combination combo = new Combination();
List<String[]> result = combo.possibleWordCombinations(goods, 4);
System.out.println(combo.words + " combination " + combo.r + ":\n");
int i = 0;
for (String[] set : result) {
System.out.println(++i + ": " + Arrays.toString(set) + ";");
}
System.out.println("\nNumber of ways is " + result.size() + ".");
}
}Try it out!
Elegance (0.0)
