CG_SuffixPrefix_1.json

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 "metadata": {
  "name": ""
 },
 "nbformat": 3,
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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import string\n",
      "\n",
      "def suffixPrefixMatch(x, y, k):\n",
      "    ''' Return length of longest suffix of x of length at least k that\n",
      "        matches a prefix of y.  Return 0 if there no suffix/prefix\n",
      "        match has length at least k. '''\n",
      "    if len(x) < k or len(y) < k:\n",
      "        return 0\n",
      "    idx = len(y) # start at the right end of y\n",
      "    # Search right-to-left in y for length-k suffix of x\n",
      "    while True:\n",
      "        hit = string.rfind(y, x[-k:], 0, idx)\n",
      "        if hit == -1: # not found\n",
      "            return 0\n",
      "        ln = hit + k\n",
      "        # See if match can be extended to include entire prefix of y\n",
      "        if x[-ln:] == y[:ln]:\n",
      "            return ln # return length of prefix\n",
      "        idx = hit + k - 1 # keep searching to left in Y\n",
      "    return -1"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 9
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# overlap is 'more'\n",
      "suffixPrefixMatch('a little more', 'more than kin', k=3)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 12,
       "text": [
        "4"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# len('more') < 5 so overlap won't be found\n",
      "suffixPrefixMatch('a little more', 'more than kin', k=5)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 13,
       "text": [
        "0"
       ]
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}

thank you for your code but I have query about rfind function what will it return or what is the source code for it