CS 10 SI Week 6 Lab Exercise Solutions

ex4find.cpp

#include <iostream>

using namespace std;

string extract_bold(string);

int main() {
  string test1 = "To <b>succeed</b> in <b>life</b> one must be <b>bold</b>!";
  cout << extract_bold(test1) << endl;

  return 0;
}

string extract_bold(string htmlText) {
  // these tags and their lengths will never change, so we'll make them const
  const string OPEN_TAG = "<b>";
  const int OPEN_LENGTH = OPEN_TAG.size();
  const string CLOSE_TAG = "</b>";
  const int CLOSE_LENGTH = CLOSE_TAG.size();

  // this string will hold our comma separated list of results 
  string results = "";
  
  // this is where we'll start searching for the next <b> tag
  int findStartIndex = 0;
  // we'll keep searching so long as there are more <b> tags in the string 
  while (htmlText.find(OPEN_TAG, findStartIndex) != -1) {
    // find the beginning and end of our next result 
    int beginIndex = htmlText.find(OPEN_TAG, findStartIndex) + OPEN_LENGTH;
    int endIndex = htmlText.find(CLOSE_TAG, findStartIndex);

    // substr expects a length, so we'll calculate the length of our next result
    int length = endIndex - beginIndex;

    // extract the next result using substring
    string nextResult = htmlText.substr(beginIndex, length);

    // append this next result (and a comma) to our results string 
    results = results + ", " + nextResult;

    // our new starting search index is after the </b> tag
    findStartIndex = endIndex + CLOSE_LENGTH;
  }

  // if there are any results, they will begin with ", " so we'll eliminate those
  if (results.size() > 0)
    results = results.substr(2);

  // return the answer
  return results;
}

ex4substr.cpp

#include <iostream>

using namespace std;

string extract_bold(string);

int main() {
  string test1 = "To <b>succeed</b> in <b>life</b> one must be <b>bold</b>!";
  cout << extract_bold(test1) << endl;

  return 0;
}

string extract_bold(string htmlText) {
  // these tags and their lengths will never change, so we'll make them const
  const string OPEN_TAG = "<b>";
  const int OPEN_LENGTH = OPEN_TAG.size();
  const string CLOSE_TAG = "</b>";
  const int CLOSE_LENGTH = CLOSE_TAG.size();

  // it is bad practice to modify parameters, so we'll use a new variable instead 
  string remainder = htmlText;

  // this string will hold our comma separated list of results 
  string results = "";
  
  // we'll keep searching so long as there are more <b> tags in the string 
  while (remainder.find(OPEN_TAG) != -1) {
    // find the beginning and end of our next result 
    int beginIndex = remainder.find(OPEN_TAG) + OPEN_LENGTH;
    int endIndex = remainder.find(CLOSE_TAG);

    // substr expects a length, so we'll calculate the length of our next result
    int length = endIndex - beginIndex;

    // extract the next result using substring
    string nextResult = remainder.substr(beginIndex, length);

    // append this next result (and a comma) to our results string 
    results = results + ", " + nextResult;

    // the remaining string we have to search is everything after the </b> tag
    remainder = remainder.substr(endIndex + CLOSE_LENGTH);
  }

  // if there are any results, they will begin with ", " so we'll eliminate those
  if (results.size() > 0)
    results = results.substr(2);

  // return the answer
  return results;
}