Snail

题目

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

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array = [[1,2,3],
         [4,5,6],
         [7,8,9]]
snail(array) #=> [1,2,3,6,9,8,7,4,5]

For better understanding, please follow the numbers of the next array consecutively:

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array = [[1,2,3],
         [8,9,4],
         [7,6,5]]
snail(array) #=> [1,2,3,4,5,6,7,8,9]

  • NOTE: The idea is not sort the elements from the lowest value to the highest; the idea is to traverse the 2-d array in a clockwise snailshell pattern.

  • NOTE 2: The 0x0 (empty matrix) is represented as en empty array inside an array [[]].

分析

看注释

答案

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let snail = function (array) {
    // 定义返回值
    let snail = [];
    while (array.length > 0) {
        // shift返回数组的第一个元素塞到结果里
        // concat弹出数组的第一个元素
        snail = snail.concat(array.shift());
        // 遍历处理后的数组，pop弹出数组的最后一个元素
        for (let i in array) {
            snail.push(array[i].pop());
        }
        //遍历处理后的数组，把数组顺序翻转
        for (let i in array) {
            array[i].reverse();
        }
        // 最后再次翻转数组
        array.reverse();
    }
    return snail;
}