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  1. import java.util.List;
  2. import java.util.LinkedList;
  3. import java.util.Arrays;
  4.  
  5. public class Main {
  6. 	public static void main (String[] args) {
  7. 		List<List<String>> input = Arrays.asList(
  8. 			Arrays.asList("England"),
  9. 			Arrays.asList("London", "Liverpool"),
  10. 			Arrays.asList("DG300", "SS500")
  11. 		);
  12.  
  13. 		for (List<String> output : combinations(input)) {
  14. 			System.out.println(output);
  15. 		}
  16. 	}
  17.  
  18. 	// combinations :: [[String]] -> [[String]]
  19. 	public static List<List<String>> combinations(List<List<String>> values) {
  20.  
  21. 	    // combinations [] = [[]]
  22. 	    if (values.isEmpty()) {
  23. 	        return Arrays.asList(Arrays.asList());
  24. 	    }
  25.  
  26. 	    // combinations (x:xs) =
  27. 	    List<String>       x  = values.get(0);
  28. 	    List<List<String>> xs = values.subList(1, values.size());
  29.  
  30. 	    // do
  31. 	    List<List<String>> outputs = new LinkedList<>();
  32.  
  33. 	    // ys <- combinations xs
  34. 	    for (List<String> ys : combinations(xs)) {
  35.  
  36. 	        // y <- x
  37. 	        for (String y : x) {
  38.  
  39. 	            // (y:ys)
  40. 	            List<String> output = new LinkedList<>();
  41. 	            output.add(y);
  42. 	            output.addAll(ys);
  43.  
  44. 	            // return
  45. 	            outputs.add(output);
  46. 	        }
  47. 	    }
  48.  
  49. 	    return outputs;
  50. 	}
  51. }
Success #stdin #stdout 0.04s 4386816KB
comments (?)
stdin 
Standard input is empty
stdout 
[England, London, DG300]
[England, Liverpool, DG300]
[England, London, SS500]
[England, Liverpool, SS500]
https://ideone.com/FyIZsn
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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