从中间出过程阵列 [英] Process array from the middle out

问题描述

我需要经过一个数组从中间outwords。

I need to go through an array from the middle outwords.

var array = [a,b,c,d,e];

我需要在这个以打印：
C，D，B，E，A

I would need to print in this order: c,d,b,e,a

我已经劈成两半的阵列，首先向前，然后倒退这已经是一个进步，但我真的需要去一边一个，直到两边的数组的结尾。

I have already split the array in half, first going forward and then going backwards which is already an improvement, but I really need to go one on each side till the end of the array on each side.

说我想在中间开始。我以前的循环语句，条件下，我似乎无法找出第三部分切换一边一个增量。

Say I want to start in the middle. I have the following before the loop statement, condition, and I can't seem to figure out the third part to switch one on each side incrementally.

for (var i = Math.floor(array.length/2); i >= 0 || i < array.length; i?){
//Do Something here.
}

有谁知道如何做到这一点？
很显然，我似乎无法在这种情况下，以测试。

Does anyone know how to do this? Obviously I can't seem to test this in this condition.

感谢

我修改下面答案（非常感谢）拿出这个功能。它允许从阵列中的任何地方开始，然后选择要去的方向。我相信它可以更文笔优美。也有对错误的索引号的安全。

I modified the answer below (Thanks so much) to come up with this function. It allows to start from anywhere in the array and choose the direction to go. I am sure it could be written more elegantly. There is also a safety for wrong index numbers.

var array = ["a", "b", "c", "d", "e"];

function processArrayMiddleOut(array, startIndex, direction){
    if (startIndex < 0){ 
        startIndex = 0;
    }
    else if ( startIndex > array.length){
        startIndex = array.lenght-1;
    };

    var newArray = [];

    var i = startIndex;

    if (direction === 'right'){
        var j = i +1;
        while (j < array.length || i >= 0 ){
            if (i >= 0) newArray.push(array[i]);
            if (j < array.length) newArray.push(array[j]);
            i--;
            j++;                
        };
    }
    else if(direction === 'left'){
        var j = i - 1;
        while (j >= 0 || i < array.length ){
            if (i < array.length) newArray.push(array[i]);
            if (j >= 0) newArray.push(array[j]);
            i++;
            j--;                
        };
    };

    return newArray;            
}    

var result = processArrayMiddleOut(array, 2, 'left');

alert(result.toString());

http://jsfiddle.net/amigoni/cqCuZ/

推荐答案

两个计数器，一个往上走，等下去：

Two counters, one going up, other going down:

var array = ["a", "b", "c", "d", "e"];
var newArray = [];

var i = Math.ceil(array.length/2);
var j = i - 1;

while (j >= 0)
{
    newArray.push(array[j--]);
    if (i < array.length) newArray.push(array[i++]);
}

http://jsfiddle.net/X9cQL/

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