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如果说“ABCDE”,那么,怎样才能把两者结合起来? 这项任务是否有一份意向书?

i.e.

"AB"
"AC"
"AD"
"AE"
"BC"
"BD"
"BE"
"CD"
"CE"
"DE"

Answer 1

private static List<String> getCombinations(String input) {
    ArrayList<String> result = new ArrayList<String>();
    int len = input == null ? 0 : input.length();
    for (int i = 0; i < len - 1; i++) {
        for (int j = i + 1; j < len; j++) {
            String combination = String.valueOf(input.charAt(i))
                    + input.charAt(j);
            System.out.println("adding: " + combination);
            result.add(combination);
        }
    }
    return result;
}

getCombinations ("ABCDE”);

adding: AB
adding: AC
adding: AD
adding: AE
adding: BC
adding: BD
adding: BE
adding: CD
adding: CE
adding: DE

Answer 2

页: 1 阅读的最佳来源是Knuth“第1卷计算机设计书的艺术”,或如:

http://webhome.csc.uvic.ca/~haron/CoolCocoon.pdf

Answer 3

i+1pseudocode:

    String alphabet = "ABCDE";
    for( int i = 0; i < alphabet.getLength(); i++){
     for( int j = alphabet.getLength(); j > i; j--){
       System.out.println( alphabet.substring(i, i+1) + alphabet.substring(j, j+1) );
     }
    }

If you need more combinations like: BA CA and so on then because there are only 2 letters you can switch the position of both of them and append the result of this process to the generated pairs. If you need combinations of three and so on then take a look on permutation algorithms.

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