如何使用 CPP 在文本文件中写入

Question

Actually, I has four dimensional data with value into a text file "fourdimensionalM.txt" and I want to read data from txt file "fourdimensionalM.txt" which has

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

and want to write into new txt file the where the four dimensional matrix has no number. I write the code but this only save zero value into value position five column but I want to write non zero value which has into txt file "fourdimensionalM.txt" and save it on new txt file.

#include <iostream>
#include<vector>
#include <stdio.h>
#include <cstdlib>
#include <ctime>
#include <fstream>
#include <sstream>

using namespace std;

int main()
{
    int X=4,Y=4,Z=4,M=4;
    /*printf("Enter size of 1st dimension X= ");
    scanf("%d",&X);
    printf("\n Enter size of 2nd dimension Y= ");
    scanf("%d",&Y);
    printf("\n Enter size of 3rd dimension Z= ");
    scanf("%d",&Z);
    printf("\n Enter size of 4th dimension M= ");
    scanf("%d",&M);
    printf("\n"); */
    srand((unsigned) time(0));
    ofstream fourDtensor;
    fourDtensor.open("fourDtensor.txt");

    ifstream four_dimension_tensor("uber3.txt");
    int a,b,c,d,vl,new_x_1,new_x_2,flag;
    cout<<"Starting"<<endl;


    for (int i = 0; i < X; i++)
    {
        //cout<<i<<endl;
        for (int j = 0; j < Y; j++)
            {
                for (int k = 0; k < Z; k++)
                {
                    for(int l=0; l < M; l++)
                    {   flag=0;
                        cout<<"before"<<endl;
                        while(!four_dimension_tensor.eof()){
                            four_dimension_tensor>>a>>b>>c>>d>>vl;
                            cout<<a<<" "<<b<<" "<<c<<" "<<d<<" "<<vl<<endl;
                                if(a==i && b==j && c==k && d==l){
                                    flag=1;
                        }

                    }
                    cout<<"after"<<endl;
                    if(flag==1){

                    fourDtensor << i<< " " << j << " " << k << " "<< l << " " << vl ;
                                    fourDtensor << endl;
                                }
                                else{
                                    fourDtensor << i<< " " << j << " " << k << " "<< l << " " << 0 ;
                                    fourDtensor << endl;
                }
            }
    }

}

    }

    return 0;

}

Answer 1

If I understand your question correctly, you are given a file with select points values for R^4 and you need to produce the full hypercube with zeroes for places where you do not have a point.

If you can assume the input file is sorted lexicographically, you can do the following:

int ti, tj, tk, tl, tv; // target coordinates and value

ifstream targets("uber3.txt");
void advance() {
  targets >> ti >> tj >> tk >> tl >> tv;
  if (targets.eof()) {
    ti = tj = tk = tk = -1;
  }
}

int get_value(int i, int j, int k, int l) {
  if (i == ti && j == tj && k == tk && l == tl) {
    // the arguments match the current target
    int ret = tv; // advance() overwrites tv, so take a copy
    advance();
    return ret;
  } else {
    return 0;
  }
}

and then the core of your main loop (ie inside the four nested for -loops) becomes simple:

fourDtensor << i << " " << j << " " << k << " " << l << " " << get_value(i,j,k,l);

Don't forget to call advance() once at the start of the program!