Dutch Flag Problem

dutchflag.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "flag = [0,1,2,0,1,1,2,0,2,1,0,0,1,1,2,2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "mid_value = 1\n",
    "low = 0\n",
    "mid = 0\n",
    "high = len(flag)-1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2]\n"
     ]
    }
   ],
   "source": [
    "while mid <= high:\n",
    "    if flag[mid] < mid_value:\n",
    "        tmp = flag[low]\n",
    "        flag[low] = flag[mid]\n",
    "        flag[mid] = tmp\n",
    "        low +=1\n",
    "        mid +=1\n",
    "    elif flag[mid] == mid_value:\n",
    "        mid +=1\n",
    "    elif flag[mid] > mid_value:\n",
    "        tmp = flag[high]\n",
    "        flag[high] = flag[mid]        \n",
    "        flag[mid] = tmp\n",
    "        high -= 1\n",
    "        \n",
    "print(flag)"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3.6",
   "language": "python",
   "name": "python36"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.6.3"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}