Question

The following is the problem I’m working on and my snippet of code.
Is there a better way to implement this? I have used basic control structures for this below.

Is it better to store the rows and columns in a map and searching through the map based on the key/value pairs?

There is a security keypad at the entrance of a building. It has 9 numbers 1 – 9 in a 3×3 matrix format.

1 2 3
4 5 6
7 8 9

The security has decided to allow one digit error for a person but that digit should be horizontal or vertical. Example: for 5 the user is allowed to enter 2, 4, 6, 8 or for 4 the user is allowed to enter 1, 5, 7. IF the security code to enter is 1478 and if the user enters 1178 he should be allowed.

The following is a snippet of code i was working on:

ArrayList<Integer> list = new ArrayList<Integer>();
int num = 9;
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};

for(int i =0;i< arr.length;i++){
  for(int j = 0; j <arr.length;j++){
    if(num == arr[i][j]){
      row = i;
      col = j;
      break;

    }
  }
}
for(int j1 = 0; j1< 3 ; j1++){
  if(arr[row][j1] != num){
    list.add(arr[row][j1]);
  }
}
for(int i1 = 0 ; i1 <3;i1++){
  if(arr[i1][col] != num){
    list.add(arr[i1][col]);
  }
}

Answer 1

There are many ways to solve this, but I think it can be solved with HashMaps and HashSets more efficiently than doing several iterations.

If I were you, I would build the data model first using a hash map and a hash set. This is because hash map and hash set have fast lookup, (no iterations)

HashMap<Integer,HashSet<Integer>> values = new HashMap<Integer, HashSet<Integer>>();

//now put in the accepted values for one
HashSet<Integer> oneValues = new HashSet<Integer>();
oneValues.put(1);
oneValues.put(2);
oneValues.put(4);
values.put(1, oneValues);

//put in 2 values
......

Then when you parse your input, if you want to see if an inputed value is accepted for what the code is, just do something like

private boolean isAccepted(int input, int combinationValue)
{
  // check to see if the inputed value in the accepted values set
  return values.get(combinationValue).contains(input);
}