dutch_national_flag.js

function national_flag(a, p) {
  function swap(i, j) {
    // console.log("swapping a[" + i + "]:" + a[i] + " a[" + j +  "]:" +  a[j]);
    var aux = a[i];
    a[i] = a[j];
    a[j] = aux;
  }

  var value = a[p];

  var i = 0;
  var k = 0;
  var j = a.length - 1;
  while(i <= j) {
    if (a[i] < value) {
      swap(i,k);
      i++;
      k++;
    } else if(a[i] > value) {
      swap(i,j);
      j--;
    } else {
      i++
    }
  }
  console.log(a)
}


national_flag([1,2,3,1,2,3,1,2,3], 1)
var a1 = [3,4,5,432,54,36,5,6,546,45,65,6,45,645,6,546,459,89,78,987,9,78];
national_flag(a1, 1)
var a2 = [1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9];
national_flag(a2, 1)
var a3 = [4,5,1,2,3,1,5,6,3,3,3,3,3,6,4, 4,5,6,4,4,5,6,4];
national_flag(a3, 1)