Stupendous February 2016

How can I compare line from text file to multiple lines following?

I have a text file with 1s, 2s and 3s like below:

1
1
2
3
3
3
1
2
2
2
2
1

..and I am trying to find a way to find out how many in a row for each.

For example if I was checking 1 it would output: 1 in a row: 2, 2 in a row: 1, 3 in a row: 0, 4 in a row: 0.... all the way to 20 in a row (array size), since there is 2 1s in a row once and then 2 1s by themselves (only 1 in a row)

I am trying to calculate HOW MANY TIMES the number 1 is only 1 in a row, 2 in a row, 3 in a row, etc up to 20 (if i had a longer list)

So far this is what I have, however I don't know what to do at the ??? line:

int main()
{
    ifstream file("test.txt");
    string linebuffer;
    int sequenceCounts[20];
    int onez = 0;

    while (file && getline(file, linebuffer)){
        if (linebuffer.length() == 0)continue;
        {
            if (linebuffer == "1")
            {
                ??? while the next is 1->onez++
                sequenceCounts[onez]++;
            }
        }

    }
    return 0;
}

Answers


Anedar February 2016

Try something along the lines of this:

int sequenceCounts[20];
int currentOnes = 0;

while (file && getline(file, linebuffer)){
  if (linebuffer.length() == 0){
    if (currentOnes > 0){
      sequenceCounts[currentOnes]++;
    }
    continue;
  }

  if (linebuffer == "1")
  {
    currentOnes++;  //We found another 1,
    //meaning the current group is bigger than in the last line.
  } else if (currentOnes > 0){
    //This line does not contain a "1", but the previous lines did
    sequenceCounts[currentOnes]++;
    currentOnes = 0;
  }
}

Basically each time you encounter a "1" you increase a counter how long your current sequence is. When the sequence is finished (a line without a "1" but with "1"s before) you increase the counter for that particular number of "1"s and reset your counter for the current sequence.

Edit: previous failed if the file ended with a "1"


Goodies February 2016

I did this using a vector and a simple map to hold the longest consecutive streak, so you'd merely have to read the lines, parse them to ints, and add them to a vector.

#include <iostream>
#include <cstdlib>
#include <vector>
#include <fstream>
#include <algorithm>
#include <map>

int mostConsec(const std::vector<int> &vec) {
    std::map<int, size_t> consecMap;
    size_t count = 0;
    int current = vec.front();
    for (auto i : vec) {
        if (consecMap.count(current) == 0)
            consecMap[current] = 0;
        if (i == current) {
            count += 1;
            if (consecMap[current] <= count)
                consecMap[current] = count;
        }
        else {
            count = 1;
        }
        current = i;
    }
    auto ptr = std::max_element(
        consecMap.begin(),
        consecMap.end(),
        [](const std::pair<int, size_t> &p1, const std::pair<int, size_t> &p2) {return p1.second < p2.second; }
    );
    return ptr->first;
}

int main(int argc, char **argv) {
    std::vector<int> v;
    std::ifstream inFile("test.txt");
    int tmp;
    while (inFile >> tmp)
        v.push_back(tmp);
    inFile.close();
    int most = mostConsec(v);
    std::cout << most << std::endl;
    system("pause");
}

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Asked in February 2016
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