JAVA组合生成器 [英] Combination Generator in JAVA

问题描述

我试图找到几个数组中的项目的所有组合。数组的数量是随机的（这可以是2,3,4,5 ...）。

例如，我有3个数组：

<$ p $ array1 = {{A1，A2，A3}，{B1，B2，B3}，{C1， C2\" }};

我想用所有可能的组合生成一个数组：

  A1，B1，C1 
 A1，B1，C2 
 A1，B2，C1 
 A1 ，B2，C2 
 A1，B3，C1 
 A1，B3，C2 
 A2，B1，C1 
 A2，B1，C2 ... 
  
 
 $ div class =h2_lin>解决方案

您可以使用counter类似的策略，即将这些数组视为一个数字的数字，如下所示：

  public static String [] [] generateCombinations String [] ... arrays）{
 if（arrays.length == 0）{
 return new String [] [] {{}}; 
} 
 int num = 1; 
 for（int i = 0; i< arrays.length; i ++）{
 num * = arrays [i] .length; 
} 
 
 String [] [] result = new String [num] [arrays.length]; 
 
 //包含字符串索引的数组
 int [] combination = new int [arrays.length]; 
 
 for（int i = 0; i< num; i ++）{
 String [] comb = result [i]; 
 // fill array 
 for（int j = 0; j  comb [j] = arrays [j] [combination [j]]; 
} 
 
 //产生下一个组合
 for（int j = arrays.length-1; j> = 0; j--）{
 int n = ++组合[j]; 
 if（n> = arrays [j] .length）{
 //digit超出了有效范围 - >返回0并继续递增
组合[j] = 0; 
} else {
 //digit仍然在有效范围内 - >停止
休息; 
} 
} 
} 
返回结果; 
 
 
 
 
 
 
该方法如下所示：
 
 
  generateCombinations（
 new String [] {A1，A2，A3}，
 new String [] {B1 ，B2，B3}，
 new String [] {C1，C2} 
）
  
或者像这样：
 
 
  generateCombinations（array1）
  code> 
 
I am trying to find all combinations of items in several arrays. The number of arrays is random (this can be 2, 3, 4, 5...). The number of elements in each array is random too.


e.g., I have the 3 arrays :
String[][] array1 = {{"A1","A2","A3"},{"B1","B2","B3"},{"C1","C2"}};
I would like to generate an array with all possible combinations :

A1, B1, C1
A1, B1, C2
A1, B2, C1
A1, B2, C2
A1, B3, C1
A1, B3, C2
A2, B1, C1
A2, B1, C2 ...


解决方案
You could create the combinations by using a "counter-like" strategy, i.e. treat those arrays as digits of a number like this:
public static String[][] generateCombinations(String[]... arrays) {
    if (arrays.length == 0) {
        return new String[][]{{}};
    }
    int num = 1;
    for (int i = 0; i < arrays.length; i++) {
        num *= arrays[i].length;
    }

    String[][] result = new String[num][arrays.length];

    // array containing the indices of the Strings
    int[] combination = new int[arrays.length];

    for (int i = 0; i < num; i++) {
        String[] comb = result[i];
        // fill array
        for (int j = 0; j < arrays.length; j++) {
            comb[j] = arrays[j][combination[j]];
        }

        // generate next combination
        for (int j = arrays.length-1; j >= 0; j--) {
            int n = ++combination[j];
            if (n >= arrays[j].length) {
                // "digit" exceeded valid range -> back to 0 and continue incrementing
                combination[j] = 0;
            } else {
                // "digit" still in valid range -> stop
                break;
            }
        }
    }
    return result;
}
The method is called like this:
generateCombinations(
            new String[]{"A1","A2","A3"},
            new String[]{"B1","B2","B3"},
            new String[]{"C1","C2"}
       )
or like this:
generateCombinations(array1)


                        
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