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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

<script id="jsbin-javascript">
function getPivot(numbers,low,high){
  if(low===high){
    return numbers[low];
  }
  var step = 5, n=-1,i=low,l=high-step,medianIndex;
  while(i<=l){
    medianIndex = getMedian(numbers,i,i+step-1);
    exchange(numbers,++n,medianIndex);
    i+=5;
  }
  if(i<=high){
    medianIndex = getMedian(numbers,i,high);
    exchange(numbers,++n,medianIndex);
  }
  return getPivot(numbers,low,n);
}

function getMedian(numbers,low,high){
  var medianIndex = Math.trunc(0.5*(high-low))+low;
  for(var i =low;i<=medianIndex;i++){
    var flag =i;
    for(var j = i+1;j<=high;j++){
      if(numbers[j]<numbers[flag]){
        flag = j;
      }
    }
    exchange(numbers,i,flag);
  }
  return medianIndex;
}
function exchange(numbers,index1,index2){
  var temp = numbers[index1];
  numbers[index1]=numbers[index2];
  numbers[index2]=temp;
}

var numbers=[1,12];
var pivot = getPivot(numbers,0,numbers.length-1);
console.log(pivot);
</script>


<script id="jsbin-source-javascript" type="text/javascript">function getPivot(numbers,low,high){
  if(low===high){
    return numbers[low];
  }
  var step = 5, n=-1,i=low,l=high-step,medianIndex;
  while(i<=l){
    medianIndex = getMedian(numbers,i,i+step-1);
    exchange(numbers,++n,medianIndex);
    i+=5;
  }
  if(i<=high){
    medianIndex = getMedian(numbers,i,high);
    exchange(numbers,++n,medianIndex);
  }
  return getPivot(numbers,low,n);
}

function getMedian(numbers,low,high){
  var medianIndex = Math.trunc(0.5*(high-low))+low;
  for(var i =low;i<=medianIndex;i++){
    var flag =i;
    for(var j = i+1;j<=high;j++){
      if(numbers[j]<numbers[flag]){
        flag = j;
      }
    }
    exchange(numbers,i,flag);
  }
  return medianIndex;
}
function exchange(numbers,index1,index2){
  var temp = numbers[index1];
  numbers[index1]=numbers[index2];
  numbers[index2]=temp;
}

var numbers=[1,12];
var pivot = getPivot(numbers,0,numbers.length-1);
console.log(pivot);</script></body>
</html>