[js]根据传入的数字，返回其中包含的最大的连续五位数

[VaJoy]

/* 
 * 根据传入的数字，返回其中包含的最大的连续五位数
 * e.g.
 * maxFiveDigits(283910356876)   // =>91035
 * maxFiveDigits(123456) //  => 23456
 */
function maxFiveDigits(num) {
  //TODO:完成该函数
}

[wsgouwan]

function maxFiveDigits(num) {
        var str = num + '',arr = [];
        if(str.length < 5){
            return
        }else{
            for( var i = 0; i < str.length - 4; i ++){
                arr.push(str.substr(i,5))
            }
        }
        return Math.max.apply(window, arr);
    }    maxFiveDigits(984574152479)

[overkazaf]

function maxFiveDigits(num) {
  //TODO:完成该函数
  num = '' + num;
  var start = num.length - 5;
  if (start < 0) throw new Error('Parameter illegal');

  var last = +num.substring(start);
  return start == 0 ? last : num.split('').reduceRight(function (pre, cur, index, array) {
                            return (index < start) ? (last = Math.max(num.substring(index, index+5), last)) : last;
                          });
}

[bluesrocker]

var num = 92999999799999;
alert( maxFiveDigits(num) );

function maxFiveDigits(num){
    num = parseInt(num);
    var reg = /\d{5}/g;
    if( !(isNaN(num)) && reg.test(num) ){
        var i = 0;
        reg.lastIndex = i;
        var matched;
        var arr = [];

        while((matched = reg.exec(num)) !== null){
            arr.push(matched[0]);
            reg.lastIndex = ++i;
        }

        arr = arr.sort(function(a, b){ return b - a;});
        var leng = arr.length;
        var result = [];
        for(var j=0; j<leng; j++){
            if(arr[0]>arr[j]){
                break;
            }
            result.push(arr[j]);
        }
        if(result.length === 1){
            return result[0];
        }
        return result;
    }
}

[langmao]

写一个

 function maxFiveDigits(num){
      num = num + "";//转换为字符

      var max = 0,//最大值
          now = 0;//当前值    

      for(var i = 0,n=num.length-4;i<n;i++){
         now = num.substring(i,i+5);//截取连续5位数

         if(now > max)//如果当前值比最大值大 交换位置
           max = now;
      }

      return max;
   }

[langmao]

来个更新，对比了几个算法的性能（假设num为字符类型----省去转换的一步）
----------------------------------------分割线------------------------------------------------

    //随机填充数据
    //生成count位的随机数
    function randomFill(count){
      var ran = []; 

      for(var i = 0 ; i < count ; i++)
        ran.push(Math.ceil(Math.random()*9));

      return ran.join("");
    }

    var num = randomFill(100000);//10万位, (如果用100万位数的话，Math.max 会报错)


    function maxFiveDigits(num){

      var max = 0,//最大值
          now = 0;//当前值    

      for(var i = 0,n=num.length-4;i<n;i++){

         now = num.substr(i,5);//截取连续5位数

         if(now > max)//如果当前值比最大值大 交换位置
           max = now;
      }

      return max;
    }

    //减少substr 调用次数
    function maxFiveDigits2(num){
      var d = num[0],
          max = num.substr(0,5),
          now = 0;
      for(var i = 1 , n = num.length - 4 ; i < n ; i ++ ){
        if ( num[i] < d )continue;

        d =num[i];

        now = num.substr(i,5);

        if( now > max )
           max = now;
      }

      return max;
    }


    //利用Math.max 比较
    function maxFiveDigits3(num) {
        var str = num + '',arr = [];
        if(str.length < 5){
            return
        }else{
            for( var i = 0; i < str.length - 4; i ++){
                arr.push(str.substr(i,5))
            }
        }
        return Math.max.apply(window, arr);
    }


   ------为了保证测试的准确性，随机调用了8次，最终 “减少substr调用次数” 的算法效率最高。------

    var start = Date.now();

    console.log(maxFiveDigits(num));

    console.log(Date.now() - start);//8ms 8ms 9ms 9ms 4ms 10ms 5ms 9ms

    start = Date.now();

    console.log(maxFiveDigits2(num));

    console.log(Date.now() - start);//7ms 6ms 6ms 6ms 5ms 6ms 5ms 5ms


    start = Date.now();

    console.log(maxFiveDigits3(num));

    console.log(Date.now() - start);//15ms 15ms 16ms 10ms 17ms 12ms 16ms 16ms

[wait-hua]

    function maxFiveDigits(num) {
        var arr = new Array();
        var str = num + "";
        if(str.length < 5) {
            return ;
        }
        var max = 0, temp1, temp2;
        for(var i=0,len=str.length; i<len-4; i++) {
            temp1 = str.substr(i, 5);
            temp2 = temp1 - '0';
            if(temp2 > max) {
                max = temp2;
            }
        }
        return max;
    }

[VaJoy]

贴个有意思的

function maxFiveDigits(num) {
  var  d = num.toString();
  var  res = 0;
  var  tmp = 0;
  for(var  i = 0; i < d.length; i++) {
    res = Math.max(res, tmp = (tmp % 10000) * 10 + Number(d[i]));
  }
  return res;
}

[SearChen]

function maxFiveDigits(num) {
  //TODO:完成该函数
  if(!num){return false;}
   num =num +'';
  var sy ='';
  for(var i = 0; i < num.length; i++){
    if(i+5 > num.length){return sy;}
    var slit = parseInt(num.substring(i ,i+5));
    if(sy > slit){
        sy = sy;
    }else{
      sy = slit;
    }
  }
}

[Jiasm]

parseInt为解决有的字符串为0开头

(() => {
  function maxFiveDigits(num, size = 5) {
    num = String(num)
    return Math.max(...new Array(-size - ~num.length).fill().map((_, index) => parseInt(num.substr(index, size))))
  }

  console.log(maxFiveDigits(283910356876))
  console.log(maxFiveDigits(123456))
})()