Code review, help improving this code to avoid duplication

Question

I working on the Sudoku puzzle, the following code works but it's easy to see that there is a lot of duplicated code. How can I optimize it? Thanks

Problem: getSection : This function should accept three arguments: a sudoku grid, and an x and y coordinate for one of the puzzle's 3x3 subgrids. The function should return an array with all the numbers in the specified subgrid.

Input example:

var puzzle = [[ 8,9,5,   7,4,2,   1,3,6 ],
             [ 2,7,1,   9,6,3,   4,8,5 ],
             [ 4,6,3,   5,8,1,   7,9,2 ],

             [ 9,3,4,   6,1,7,   2,5,8 ],
             [ 5,1,7,   2,3,8,   9,6,4 ],
             [ 6,8,2,   4,5,9,   3,7,1 ],

             [ 1,5,9,   8,7,4,   6,2,3 ],
             [ 7,4,6,   3,2,5,   8,1,9 ],
             [ 3,2,8,   1,9,6,   5,4,7 ]];

Output:

getSection(puzzle, 0, 0);
// -> [ 8,9,5,2,7,1,4,6,3 ]

Solution:

 function getSection(arr, x, y) {
    var section = [];

    if (y === 0) {
        arr = arr.slice(0, 3);
        if (x === 0) {
            arr.forEach(function (element) {
                section.push(element.slice(0, 3));
            })
        } else if (x === 1) {
            arr.forEach(function (element) {
                section.push(element.slice(3, 6));
            })
        } else {
            arr.forEach(function (element) {
                section.push(element.slice(6, 9));
            })
        }
    }


    if (y === 1) {
        arr = arr.slice(4, 7);
        if (x === 0) {
            arr.forEach(function (element) {
                section.push(element.slice(0, 3));
            })
        } else if (x === 1) {
            arr.forEach(function (element) {
                section.push(element.slice(3, 6));
            })
        } else {
            arr.forEach(function (element) {
                section.push(element.slice(6, 9));
            })
        }
    }

    if (y === 2) {
        arr = arr.slice(6, 9);
        if (x === 0) {
            arr.forEach(function (element) {
                section.push(element.slice(0, 3));
            })
        } else if (x === 1) {
            arr.forEach(function (element) {
                section.push(element.slice(3, 6));
            })
        } else {
            arr.forEach(function (element) {
                section.push(elemet.slice(6, 9));
            })
        }
    }
    var subgrid = section.reduce(function (a, b) {
        return a.concat(b);
    },
        []
    );
    return subgrid;

}

console.log(getSection(puzzle, 0, 0));
// // -> [ 8,9,5,2,7,1,4,6,3 ]

console.log(getSection(puzzle, 1, 0));
// -> [ 7,4,2,9,6,3,5,8,1 ]

Answer 1

Here's my take using ES6

 const puzzle = [ [8, 9, 5, 7, 4, 2, 1, 3, 6], [2, 7, 1, 9, 6, 3, 4, 8, 5], [4, 6, 3, 5, 8, 1, 7, 9, 2], [9, 3, 4, 6, 1, 7, 2, 5, 8], [5, 1, 7, 2, 3, 8, 9, 6, 4], [6, 8, 2, 4, 5, 9, 3, 7, 1], [1, 5, 9, 8, 7, 4, 6, 2, 3], [7, 4, 6, 3, 2, 5, 8, 1, 9], [3, 2, 8, 1, 9, 6, 5, 4, 7] ]; const GRID_SIZE = 3; function getOffset(coordinate) { const start = coordinate * GRID_SIZE; const end = start + GRID_SIZE; return [start, end]; } function getSection(arr, x, y) { const yOffset = getOffset(y); const xOffset = getOffset(x); const elements = arr.slice(...yOffset); return elements .map(element => element.slice(...xOffset)) .reduce((subgrid, grid) => [...subgrid, ...grid], []); } console.log(getSection(puzzle, 0, 0)); // // -> [ 8,9,5,2,7,1,4,6,3 ] console.log(getSection(puzzle, 1, 0)); // -> [ 7,4,2,9,6,3,5,8,1 ] 

Answer 2

Not as elegant as @nutboltu but almost as concise.

function getSection(arr, x, y) {
    var section = [];

    z = (y===0?0:y+y+2);
    arr = arr.slice(z, z+3);
    arr.forEach(function (element) {
        section.push(element.slice(z, z+3));
    })
    var subgrid = section.reduce(function (a, b) {
        return a.concat(b);
    },
        []
    );
    return subgrid;
}

Answer 3

I assume your x and y will not exceed your array length. Here's the simplest way to achieve the solution.

function getSection(arr, x, y) {
  var GRID_SIZE = 3;
  var indexX = x*GRID_SIZE;
  var indexY = y*GRID_SIZE;
  var results = [];
  for(var i = indexY; i< indexY+GRID_SIZE; i++){
    results = results.concat(puzzle[i].slice(indexX, indexX+GRID_SIZE));
  }
  return results;
}

console.log(getSection(puzzle, 0, 0));
// // -> [ 8,9,5,2,7,1,4,6,3 ]

console.log(getSection(puzzle, 1, 0));
// -> [ 7,4,2,9,6,3,5,8,1 ]