从fstream中的文本读取直到某行

Question

This is is my first question in stackoverflow. I am currently doing an assignment in reading an overall stats in a text file by only using string and vectors and fstream.

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

struct weather{
    string year,month,sky,mintemp,maxtemp,totrain,y, date;
    int rain = 0,scatter = 0,partly = 0,fog = 0,clean = 0,snow = 0, most =     0,storm = 0,cast = 0;
};

int main(){
string year;
int entry = 0;
vector<weather>vw;
weather w;
ifstream w_file;
w_file.open("weather.txt");
while (w_file >> w.date >> w.sky >> w.mintemp >> w.maxtemp >> w.totrain){
    year = w.date.substr(0,4);
    cout << year << endl;

 }
 cout << entry ; //this was just to confirm how many line i have in the file

what I manage to print out was the years of the file. What i wanted to do is to read the data in a specific year and print out the particular year with its contents. is there anyway I can do this without using goto?

---

 2012-01-01 Rain 7 13 0.28 2012-01-02 ScatteredClouds 4 8 0.25 2012-01-03 Rain 6 12 0.28 2012-01-04 Rain 5 10 0.28 2012-01-05 Rain 7 12 0.28 2012-01-06 PartlyCloudy 3 9 0.28 2012-01-07 PartlyCloudy 7 11 0.25 2012-01-08 Rain 7 10 0.28 2012-01-09 PartlyCloudy 6 12 0.25 2013-01-01 Rain 3 8 0.28 2013-01-02 Rain 2 11 0.25 2013-01-03 PartlyCloudy 9 11 0.28 2013-01-04 PartlyCloudy 8 10 0.28 

---

 year = 2012 rain = 0//rain++ if rain is found partlyCloudy = 0//partly++ if partlyCloudy is found year = 2013 rain = 0//rain++ if rain is found partlyCloudy = 0//partly++ if partlyCloudy is found 

Answer 1

Of course there's a way to do this without using goto . I can't think of any case where goto is required anymore.

Look into iterating through your vector. A good reference is http://www.cplusplus.com/reference/vector/vector/begin/

The code snippet example from there is:

#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myvector;
  for (int i=1; i<=5; i++) myvector.push_back(i);

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it = myvector.begin() ; it != myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

In your case, you'll want to check each *it for a matching date, and then if the date matches, output the data you want from the appropriate structure.

Or, depending on how the specific date you're looking for is entered, you can put it in your existing while loop and not even bother with storing the other data in a vector . In that case, your while loop may look something like:

while (w_file >> w.date >> w.sky >> w.mintemp >> w.maxtemp >> w.totrain){
    year = w.date.substr(0,4);
    if (year == "1974") { // or whatever the year your looking for is...
    cout << w.date << w.sky << w.mintemp << w.maxtemp << w.totrain << endl;
}

Given the comments you've put in below, your code is on the right track - you've read in the entire file, and have the data available to manipulate it. What you now want is to track year, rain and partlyCloudy. The easiest way to do that is to make another structure, and store it in a vector. The structure would be something like this:

struct yeardata {
    string year; // could also be int, if you want to convert it to an ant
    int numberOfRain;
    int numberOfPartlyCloudy;
}

Then, when you iterate through vw (or, as you read the file. You still don't really need the vw vector), you'll have a vector of yeardatas. Check the vector to see if the year exists, and if it doesn't add it, with the two int s set to 0. Then, increment the ints as appropriate, and print out all the data from that vector.

Since it's an assignment, that's pretty much as far as I can take you. Good luck!