CodeWars 上面的奇葩问题和回答（一）

摘要：其实昨天晚上我看到最逗得一段代码是这样的，老外的创造力真是震古烁今啊，题目是写一个函数查找素数。

这两天有点迷Codewars ， 这上面的好处是奖励系统，我为了升段位晚上像打游戏升级一样的在做js习题，想想老外哪怕这简单网站的任务系统做的可真够好啊。

先给大家介绍第一道 六段题（一共8kyu，kyu上面还有dan，数字越小越难）

创造一个函数，返回如下这么个玩意，参数是圣诞树的高度，为0-100的整数，空白都需要space填充。

    *    
   ***   
  *****  
 ******* 
*********

我懵了啊，尼玛人干事？六段就这么难，但我不服输啊，于是我左思右想啊，拿出笔纸画啊，终于功夫不负有心人，被我弄出来了：

function christmasTree(height) {
  var str = "";
  var h = height;
  var w = 2*h-1;

  for(var i = 1;i<=h; i++){  
      for(var j = 1;j<=w;j++){
          if(j<=h-i || j > w - (h-i) ){
            str += " "
          }else{
            str += "*"
          }
      }
      if(i != h ) str += "
"
    }
    return str
}

我的思路是，矩阵，两个循环，判断何时放空格何时放*

信心满满的提交，我想解法都不过如此吧，不过看到老外们的答案，我震惊了，我感受到这个世界满满的恶意。。。

function christmasTree(height,shift) {
  var shift=shift||0, spaces=new Array(shift+1).join(" ");
  return height>0?(height>1?christmasTree(height-1,shift+1)+"
":"")+spaces+new Array(2*height).join("*")+spaces:"";
}

尼玛？为毛这么短，你传个shift是几个意思啊，你三项套三项还让不让人读了？

继续看：

function christmasTree(height) {
  var tree = [];
  for (var i = 1; i <= height; i++) {
    var s = "";
    for (var j = 0; j < height-i; j++) s += " ";
    for (var j = 0; j < i*2-1; j++) s += "*";
    for (var j = 0; j < height-i; j++) s += " ";
    tree.push(s);
  }
  return tree.join("
");
}

嗯，这个作者的思路跟我略像，不愧是英雄所见略同，不过，或许比我稍微简洁一些？循环里套三次循环不太好吧。

function christmasTree(height) {
  var tree = "";
  if(height > 1){
    tree = " " + 
    christmasTree(height-1)
    .split("
")
    .join(" 
 ")
    + " 
";
  }
  return tree + Array(2*(height-1)+2).join("*");

}

这个略凶啊，递归出来的？然后最后join了个* 是什么情况啊。

好吧，坚强的我并未受到打击，直到我看到了投票第一的答案，我知道原来代码是用来玩的，喃们感受一下：

/*  Merry Christmas!  */

           c=
        function
      (h){t=[];for
     (i=1;i<=h;++i,
    t.push(b))for(b=
   "",j=0;j<2*h-1;++j
  )b+=j>=h-i&&j

这叫以其人之道还治其人之身吗？这居然也能跑，为了造型把函数名拆开了啊喂，这是怎么运行的呢啊喂。你们赢了，把球给我我回家。


其实昨天晚上我看到最逗得一段代码是这样的，老外的创造力真是震古烁今啊，题目是写一个函数查找素数。

文艺青年写法：

function isPrime(num) {
  return num>1 && (new Array(Math.floor(Math.pow(num, .5)))).join(" ").split("").every(function(e,i) { return num%(i+2)!=0; }); 
}


普通青年写法：

function isPrime(num) {
  if (num < 2) return false;
  for (var i = 2; i <= Math.sqrt(num); i++)
    if (num%i == 0) return false;
  return true;
}


下面隆重登场的铅笔青年是这样写的，这货得了4票了哦：

primeList = [2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009,1013,1019,1021,1031,1033,1039,1049,1051,1061,1063,1069,1087,1091,1093,1097,1103,1109,1117,1123,1129,1151,1153,1163,1171,1181,1187,1193,1201,1213,1217,1223,1229,1231,1237,1249,1259,1277,1279,1283,1289,1291,1297,1301,1303,1307,1319,1321,1327,1361,1367,1373,1381,1399,1409,1423,1427,1429,1433,1439,1447,1451,1453,1459,1471,1481,1483,1487,1489,1493,1499,1511,1523,1531,1543,1549,1553,1559,1567,1571,1579,1583,1597,1601,1607,1609,1613,1619,1621,1627,1637,1657,1663,1667,1669,1693,1697,1699,1709,1721,1723,1733,1741,1747,1753,1759,1777,1783,1787,1789,1801,1811,1823,1831,1847,1861,1867,1871,1873,1877,1879,1889,1901,1907,1913,1931,1933,1949,1951,1973,1979,1987,1993,1997,1999,2003,2011,2017,2027,2029,2039,2053,2063,2069,2081,2083,2087,2089,2099,2111,2113,2129,2131,2137,2141,2143,2153,2161,2179,2203,2207,2213,2221,2237,2239,2243,2251,2267,2269,2273,2281,2287,2293,2297,2309,2311,2333,2339,2341,2347,2351,2357,2371,2377,2381,2383,2389,2393,2399,2411,2417,2423,2437,2441,2447,2459,2467,2473,2477,2503,2521,2531,2539,2543,2549,2551,2557,2579,2591,2593,2609,2617,2621,2633,2647,2657,2659,2663,2671,2677,2683,2687,2689,2693,2699,2707,2711,2713,2719,2729,2731,2741,2749,2753,2767,2777,2789,2791,2797,2801,2803,2819,2833,2837,2843,2851,2857,2861,2879,2887,2897,2903,2909,2917,2927,2939,2953,2957,2963,2969,2971,2999,3001,3011,3019,3023,3037,3041,3049,3061,3067,3079,3083,3089,3109,3119,3121,3137,3163,3167,3169,3181,3187,3191,3203,3209,3217,3221,3229,3251,3253,3257,3259,3271,3299,3301,3307,3313,3319,3323,3329,3331,3343,3347,3359,3361,3371,3373,3389,3391,3407,3413,3433,3449,3457,3461,3463,3467,3469,3491,3499,3511,3517,3527,3529,3533,3539,3541,3547,3557,3559,3571,3581,3583,3593,3607,3613,3617,3623,3631,3637,3643,3659,3671,3673,3677,3691,3697,3701,3709,3719,3727,3733,3739,3761,3767,3769,3779,3793,3797,3803,3821,3823,3833,3847,3851,3853,3863,3877,3881,3889,3907,3911,3917,3919,3923,3929,3931,3943,3947,3967,3989,4001,4003,4007,4013,4019,4021,4027,4049,4051,4057,4073,4079,4091,4093,4099,4111,4127,4129,4133,4139,4153,4157,4159,4177,4201,4211,4217,4219,4229,4231,4241,4243,4253,4259,4261,4271,4273,4283,4289,4297,4327,4337,4339,4349,4357,4363,4373,4391,4397,4409,4421,4423,4441,4447,4451,4457,4463,4481,4483,4493,4507,4513,4517,4519,4523,4547,4549,4561,4567,4583,4591,4597,4603,4621,4637,4639,4643,4649,4651,4657,4663,4673,4679,4691,4703,4721,4723,4729,4733,4751,4759,4783,4787,4789,4793,4799,4801,4813,4817,4831,4861,4871,4877,4889,4903,4909,4919,4931,4933,4937,4943,4951,4957,4967,4969,4973,4987,4993,4999,5003,5009,5011,5021,5023,5039,5051,5059,5077,5081,5087,5099,5101,5107,5113,5119,5147,5153,5167,5171,5179,5189,5197,5209,5227,5231,5233,5237,5261,5273,5279,5281,5297,5303,5309,5323,5333,5347,5351,5381,5387,5393,5399,5407,5413,5417,5419,5431,5437,5441,5443,5449,5471,5477,5479,5483,5501,5503,5507,5519,5521,5527,5531,5557,5563,5569,5573,5581,5591,5623,5639,5641,5647,5651,5653,5657,5659,5669,5683,5689,5693,5701,5711,5717,5737,5741,5743,5749,5779,5783,5791,5801,5807,5813,5821,5827,5839,5843,5849,5851,5857,5861,5867,5869,5879,5881,5897,5903,5923,5927,5939,5953,5981,5987,6007,6011,6029,6037,6043,6047,6053,6067,6073,6079,6089,6091,6101,6113,6121,6131,6133,6143,6151,6163,6173,6197,6199,6203,6211,6217,6221,6229,6247,6257,6263,6269,6271,6277,6287,6299,6301,6311,6317,6323,6329,6337,6343,6353,6359,6361,6367,6373,6379,6389,6397,6421,6427,6449,6451,6469,6473,6481,6491,6521,6529,6547,6551,6553,6563,6569,6571,6577,6581,6599,6607,6619,6637,6653,6659,6661,6673,6679,6689,6691,6701,6703,6709,6719,6733,6737,6761,6763,6779,6781,6791,6793,6803,6823,6827,6829,6833,6841,6857,6863,6869,6871,6883,6899,6907,6911,6917,6947,6949,6959,6961,6967,6971,6977,6983,6991,6997,7001,7013,7019,7027,7039,7043,7057,7069,7079,7103,7109,7121,7127,7129,7151,7159,7177,7187,7193,7207,7211,7213,7219,7229,7237,7243,7247,7253,7283,7297,7307,7309,7321,7331,7333,7349,7351,7369,7393,7411,7417,7433,7451,7457,7459,7477,7481,7487,7489,7499,7507,7517,7523,7529,7537,7541,7547,7549,7559,7561,7573,7577,7583,7589,7591,7603,7607,7621,7639,7643,7649,7669,7673,7681,7687,7691,7699,7703,7717,7723,7727,7741,7753,7757,7759,7789,7793,7817,7823,7829,7841,7853,7867,7873,7877,7879,7883,7901,7907,7919]
function isPrime(num) {
return (primeList.indexOf(num) != -1)
}


看到了没，你确定这样可以过check？是的！sf快卡死了，看来这篇文章要终止了。