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Search in n two-dimensional arrays

Help on how to implement a search on n 2-dimensional arrays. To be more specific: If I have 6 tables and I put them in a two-dimensional array. I will put a value, for example 10, for example, as val = 0. I need to search from these tables for all combination values ​​of 10. The value will be calculated taking into account the values ​​from all these tables.

public static int Main() {
  int[] a = {2,1,4,7};
  int[] b = {3,-3,-8,0};
  int[] c = {-1,-4,-7,6};
  int sum;
  int i; int j;  int k;
  int val = 0;
  for(i = 0; i < 4; i++) {
    for(j = 0;j<4;j++) {
      for(k = 0;k<4;k++) {
        sum = a[i]* b[j]* c[k];

        if(sum == val)
          System.out.printf("%d  %d  %d\n",a[i],b[j],c[k]);
      }
    }
  }
}
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2 answers

You can consider the table as a list of values. Then, if you have N tables, your task is to find lists of N integers (each taken from one of N tables), the product of which is equal to p. You can solve the problem recursively:

  • given a non-empty list of tables {t1, t2, t3, ...}
  • p,
  • v t1 p / v {t2, t3, ...} ( , p % v == 0,
  • .

java:

public class SO6026472 {

    public static void main(String[] args) {
        // define individual tables
        Integer[] t1 = new Integer[] {2,-2,4,7};
        Integer[] t2 = new Integer[] {3,-3,-8,0};
        Integer[] t3 = new Integer[] {-1,-4,-7,6};
        Integer[] t4 = new Integer[] {1,5};
        // build list of tables
        List<List<Integer>> tables = new ArrayList<List<Integer>>();
        tables.add(Arrays.asList(t1));
        tables.add(Arrays.asList(t2));
        tables.add(Arrays.asList(t3));
        tables.add(Arrays.asList(t4));
        // find solutions
        SO6026472 c = new SO6026472();
        List<List<Integer>> solutions = c.find(36, tables);
        for (List<Integer> solution : solutions) {
            System.out.println(
                    Arrays.toString(solution.toArray(new Integer[0])));
        }
    }

    /**
     * Computes the ways of computing p as a product of elements taken from 
     * every table in tables.
     * 
     * @param p the target product value
     * @param tables the list of tables
     * @return the list of combinations of elements (one from each table) whose
     * product is equal to p
     */
    public List<List<Integer>> find(int p, List<List<Integer>> tables) {
        List<List<Integer>> solutions = new ArrayList<List<Integer>>();
        // if we have no tables, then we are done
        if (tables.size() == 0)
            return solutions;
        // if we have just one table, then we just have to check if it contains p
        if (tables.size() == 1) {
            if (tables.get(0).contains(p)) {
                List<Integer> solution = new ArrayList<Integer>();
                solution.add(p);
                solutions.add(solution);
                return solutions;
            } else
                return solutions;
        }
        // if we have several tables, then we take the first table T, and for
        // every value v in T we search for (p / v) in the rest of the tables;
        // we do this only if p % v is equal to 0, because we're dealing with
        // ints
        List<Integer> table = tables.remove(0);
        for (Integer value : table) {
            if (value != 0 && p % value == 0) {
                List<List<Integer>> subSolutions = find(p / value, tables);
                if (! subSolutions.isEmpty()) {
                    for (List<Integer> subSolution : subSolutions) {
                        subSolution.add(0, value);
                    }
                    solutions.addAll(subSolutions);
                }
            }
        }
        tables.add(0, table);
        return solutions;
    }

}

:

[2, 3, 6, 1]
[-2, -3, 6, 1]

. , , memoization . , .

0

, :

( , )

private ArrayList numbers = new ArrayList();

public void CalculateSum(int tableNumber)
{
    if(!Tables.isLast(tableNumber))
    {
        int[][] a = Tables.Get(tableNumber);
        for(int y = 0; y < a.length; y++)
        {
            for(int x = 0; x < a[y].length; x++)
            {
                numbers.add(a[y][x]);
                CalculateSum(tableNumber + 1);
                numbers.remove(tableNumber - 1);
            }
        }
    }else
    {
        int[][] a = Tables.Get(tableNumber);
        for(int y = 0; y < a.length; y++)
        {
            for(int x = 0; x < a[y].length; x++)
            {
                if((sum(numbers) + a[y][x]) == checkValue)
                {
                    PrintNumbers(numbers);
                    System.out.print(a[y][x]);
                    System.out.println();
                }
            }
        }
    }        
}

write ( " " ):

boolean isLast (int tableNo): ,

int [] [] Get (int tableNo):

ArrayList. PrintNumbers ArrayList . checkValue - , .

, ...

, , - .

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