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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		System.out.println(letterCombinations("23"));
  13. 	}
  14.  
  15. 	private static final String[] KEYS = { "", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" };
  16.  
  17.     	public static List<String> letterCombinations(String digits) {
  18.     		List<String> ret = new LinkedList<String>();
  19.     		combination("", digits, 0, ret);
  20.     		return ret;
  21.     	}
  22.  
  23.     	private static void combination(String prefix, String digits, int offset, List<String> ret) {
  24.     		if (offset >= digits.length()) {
  25.     			ret.add(prefix);
  26.     			return;
  27.     		}
  28.     		String letters = KEYS[(digits.charAt(offset) - '0')];
  29.     		for (int i = 0; i < letters.length(); i++) {
  30.     			combination(prefix + letters.charAt(i), digits, offset + 1, ret);
  31.     		}
  32.     	}
  33. }
Success #stdin #stdout 0.07s 2184192KB
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Standard input is empty
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[ad, ae, af, bd, be, bf, cd, ce, cf]
https://ideone.com/4FodC8
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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