Snail Sort

Given an n x n array, return the array elements arranged from outermost elements to the middle element, traveling clockwise.

var array = [[1,2,3],
             [4,5,6],
             [7,8,9]]
console.log(snail(array));// [1,2,3,6,9,8,7,4,5]

• my answer

• forEach() 方法用于调用数组的每个元素，并将元素传递给回调函数。

  note: forEach() 对于空数组是不会执行回调函数的

function snail(array) {  
  var results = [];  
  while(array.length > 0) {
      results = results.concat(array.shift());    
      array.forEach(function (currentValue) {
        results.push(currentValue.pop());
      });   
      array.forEach(function (currentValue) {
        currentValue.reverse();
      });    
      array.reverse();
  }  
  return results;
}

  other answer

function snail(array) {
    var answer = [];
    for (var size = array.length, i = 0, j = 0; size > 0; size -= 2, ++j) {
        for (var k = 0; k < size - 1; ++k, ++j) answer.push(array[i][j]);
        for (var k = 0; k < size - 1; ++k, ++i) answer.push(array[i][j]);
        for (var k = 0; k < size - 1; ++k, --j) answer.push(array[i][j]);
        for (var k = 0; k < size - 2; ++k, --i) answer.push(array[i][j]);
        if (array[i][j])                        answer.push(array[i][j]);
    }
    return answer;
}