Codefights

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Different Squares

Description

Given a rectangular matrix containing only digits, calculate the number of different 2 × 2 squares in it.

Example

For

matrix = [[1, 2, 1], [2, 2, 2], [2, 2, 2], [1, 2, 3], [2, 2, 1]]

the output should be differentSquares(matrix) = 6.

Here are all 6 different 2 × 2 squares:

  • 1 2
    2 2
  • 2 1
    2 2
  • 2 2
    2 2
  • 2 2
    1 2
  • 2 2
    2 3
  • 2 3
    2 1

Input/Output

  • [execution time limit] 4 seconds (js)

  • [input] array.array.integer matrix

    Guaranteed constraints:
    1 ≤ matrix.length ≤ 100,
    1 ≤ matrix[i].length ≤ 100,
    0 ≤ matrix[i][j] ≤ 9.

  • [output] integer

    • The number of different 2 × 2 squares in matrix.

[JavaScript (ES6)] Syntax Tips

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// Prints help message to the console
// Returns a string
function helloWorld(name) {
console.log("This prints to the console when you Run Tests");
return "Hello, " + name;
}

Solution

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function differentSquares(matrix) {
  var acc = {};
  for (var i = 0; i < matrix.length - 1; i++) {
    for (var j = 0; j < matrix[i].length - 1; j++) {
      var square = matrix.slice(i, i + 2).map(r => r.slice(j, j + 2));
      acc[square[0].join("") + square[1].join("")] = 1;
    }
  }
  var ret = 0;
  for (var f in acc) {
    ret += acc[f];
  }
  return ret;
}