400. Nth Digit.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...\n",
    "\n",
    "Note:\n",
    "n is positive and will fit within the range of a 32-bit signed integer (n < 231).\n",
    "\n",
    "Example 1:\n",
    "\n",
    "Input:\n",
    "3\n",
    "\n",
    "Output:\n",
    "3\n",
    "Example 2:\n",
    "\n",
    "Input:\n",
    "11\n",
    "\n",
    "Output:\n",
    "0\n",
    "\n",
    "Explanation:\n",
    "The 11th digit of the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... is a 0, which is part of the number 10."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class Solution(object):\n",
    "    def findNthDigit(self, n):\n",
    "        \"\"\"\n",
    "        :type n: int\n",
    "        :rtype: int\n",
    "        \"\"\"\n",
    "        c=0\n",
    "        left=n\n",
    "        t=n-9*(10**c)\n",
    "        while t>0:\n",
    "            left=t\n",
    "            c+=1\n",
    "            t=t-9*(10**c)*(c+1)\n",
    "        i=(left+c)//(c+1)\n",
    "        return int(str(10**c+i-1)[(left%(c+1))-1])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "s=Solution()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "b=123"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "s.findNthDigit(2891)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "225"
      ]
     },
     "execution_count": 30,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python [default]",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.5.2"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 1
}