Repeat a string repeat a string(算法 初级)

May 25th, 2017

https://www.freecodecamp.cn/challenges/repeat-a-string-repeat-a-string

解法

解法 一 （推荐效率高）

   function repeat(pattern, count) {
     // repeat after me
     if (count < 1) return '';
       var result = '';
       while (count > 1) {
           if (count & 1) result += pattern;
           count >>= 1, pattern += pattern;
       }
       return result + pattern;
   }
   
   repeat("abc", 4);

解法二 （效率也高）

http://www.webreference.com/programming/javascript/jkm3/3.html

function repeat(x, n) {
  // repeat after me
    var s = ''; 
  if(n<1) return s;
    for (;;) { 
        if (n & 1) s += x; 
        n >>= 1; 
        if (n) x += x; 
        else break; 
    } 
    return s; 
}

repeat("abc", 4);

解法 三

This answer is old and and not terribly practical - it’s just “clever” because it uses Array stuff to get String things done. When I wrote “less process” I definitely meant “less code” because, as others have noted in subsequent answers, it performs like a pig. So don’t use it if speed matters to you.

function repeat(str, num) {
  // repeat after me
  if(num<1){
    return '';
  }else{
         return new Array( num + 1 ).join( str );
  }

}

repeat("abc", 3);

解法四

function repeat(str, num) {
  // repeat after me
  if ( num < 1) {
    return "";
  }else {
    return str.repeat(num);
  }

}

repeat("abc", 3);

Demi_YuHongJun

Demi的随笔和技术空间