DESCRIPTION

Write a function dirReduc which will take an array of strings and returns an array of strings with the needless directions removed (W<->E or S<->N side by side).

The Haskell version takes a list of directions with data Direction = North | East | West | South. The Clojure version returns nil when the path is reduced to nothing. The Rust version takes a slice of enum Direction {North, East, West, South}.

详细描述可以查看文档底部的引用链接。

SOLUTION

• 方法一：模拟栈的方式。

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function dirReduc(arr) {
  const opposites = {
    NORTH: "SOUTH",
    SOUTH: "NORTH",
    EAST: "WEST",
    WEST: "EAST",
  };
  // 创建一个数组用来模拟一个栈，用于跟踪方向
  const stack = [];
  // 遍历输入的方向数组
  for (const direction of arr) {
    // 获取当前方向的反方向
    const opposite = opposites[direction];
    // 如果栈顶方向等于当前方向的反方向，则弹出栈顶方向
    if (stack[stack.length - 1] === opposite) {
      stack.pop();
    } else {
      // 否则，将当前方向压入栈顶
      stack.push(direction);
    }
  }
  // 最终，栈中剩下的方向就是去掉不必要的相反方向后的结果
  return stack;
}

DESCRIPTION

Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.

Example

createPhoneNumber([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) // => returns "(123) 456-7890"

The returned format must be correct in order to complete this challenge.

Don’t forget the space after the closing parentheses!

SOLUTION

• 方法一：数组的 slice() 方法

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function createPhoneNumber(numbers) {
  // Create an array of the different parts of the phone number
  const areaCode = `(${numbers.slice(0, 3).join("")})`;
  const prefix = numbers.slice(3, 6).join("");
  const suffix = numbers.slice(6, 10).join("");

  // Combine the parts into the final phone number string
  const phoneNumber = `${areaCode} ${prefix}-${suffix}`;

  return phoneNumber;
}

DESCRIPTION

Your goal in this kata is to implement a difference function, which subtracts one list from another and returns the result.

It should remove all values from list a, which are present in list b keeping their order.

arrayDiff([1,2],[1]) == [2]

If a value is present in b, all of its occurrences must be removed from the other:

arrayDiff([1,2,2,2,3],[2]) == [1,3]

SOLUTION

• 方法一：

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function arrDiff(a, b) {
  return a.filter((item) => !b.includes(item));
}

DESCRIPTION

Given an integral number, determine if it’s a square number:

In mathematics, a square number or perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself.

The tests will always use some integral number, so don’t worry about that in dynamic typed languages.

Examples

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-1  =>  false
 0  =>  true
 3  =>  false
 4  =>  true
25  =>  true
26  =>  false

SOLUTION

• 方法一：

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var isSquare = function (n) {
  // 求平方根并取整
  let roundSqrt = Math.round(Math.sqrt(n));
  // 判断平方根相乘的结果是否与传入的数值相等
  return n === roundSqrt * roundSqrt;
};

DESCRIPTION

In this kata you will create a function that takes a list of non-negative integers and strings and returns a new list with the strings filtered out.

Example

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filter_list([1, 2, "a", "b"]) == [1, 2];
filter_list([1, "a", "b", 0, 15]) == [1, 0, 15];
filter_list([1, 2, "aasf", "1", "123", 123]) == [1, 2, 123];

SOLUTION

• 数组的 filter() 方法

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function filter_list(l) {
  // Return a new array with the strings filtered out
  return l.filter((word) => typeof word === "number");
}