I have a text file that looks like

6
0 0 0 
1 1 0
2 1 1
3 3 1
4 3 5
5 4 6

The first number tells the program how many rows of numbers come after it. How can I read in the first number for n, then read in the rest? When I remove the "fin>>n" and the "6" from the text file, the code works correctly. My code for this section looks like

if ( ! fin.is_open() ) {
cout<< "error opening file" << endl;
return 1;
}
else{
  fin>>n;
 for (int i=0; i<n; i  ){
 fin>> time[i] >> x[i] >> y[i];}

CodePudding user response：

You can use std::vector and std::getline for achieving this as shown below:

#include <iostream>
#include <sstream>
#include <fstream>
#include <vector>
int main()
{
    std::ifstream inputFile("input.txt");
    std::vector<int> time,x,y; 
    std::string line,tempRows;
    int rows;
    if(inputFile)
    {
        //get first value 
        std::getline(inputFile, tempRows);
        std::istringstream ss(tempRows);
        ss >> rows;
        
        //resize the vectors
        time.resize(rows);
        x.resize(rows);
        y.resize(rows);
        int i = 0;
       while(std::getline(inputFile, line) && (i < rows))//read line by line
            {
                std::istringstream ss2(line);
                ss2 >> time[i];
                ss2 >> x[i];
                ss2 >> y[i];
                  i;
            }
    }
    else 
    {
        std::cout<<"File cannot be opened";
    }
    //lets print out the elements of the vectors to confirm that we have read the values correctly
    for(int i = 0; i < rows;   i)
    {
        std::cout<< time[i] <<" "<<x[i] <<" "<<y[i]<<std::endl;
    }

    return 0;
}

The output of the program can be seen here.

CodePudding user response：

Try using scanf().

int a;
scanf("%d", &a);
for (int i = 0; i < a; i  ) {
    scanf("%d %d %d", &myVar1, &myVar2, &myVar3);
}