Accessing specific column / row and compare to another (C++) - c++

Question

I'm attempting to take a text file as an input with, let's say, six columns and twenty rows and make various calculations based on the data in the text file.
Is there a way to be able to access a specific column/row in the code and compare it to another? I'm basically trying to see how many numbers in, let's say, column two are +10 away from each other so if column two was 10 11 16 20 21 25 30 31 34 40 50, the program would give me the solution 10,20,30,40,50 and 11,21,31.

Answer 1

It sounds like you may want to utilize this functionality to do more than just figure out if numbers in a row are a set distance from eachother, so I'll provide a more generalized solution.
First create a 20x6 matrix of character pointers:
char *inputmatrix[20][6];
Then load up the matrix with the values from the file. We first get the whole line from the file with fgets, from there we need to parse the line based on spaces using strtok. From there we'll need to create space for each element using malloc, copy in the value from strtok (because it gets overridden on the next call to strtok), and then store the pointer in our array:
char buffer[256];
char *value;
while(!feof(f)){
if(!fgets(buffer,256,f))
break;
value = strtok(buffer," ");
while(value != NULL){
inputmatrix[currow][curcol] = (char*)malloc(strlen(value+1));
memset(inputmatrix[currow][curcol],0,strlen(value+1));
memcpy(inputmatrix[currow][curcol],value,strlen(value));
curcol++;
value = strtok(NULL," ");
}
currow++;
curcol = 0;
}
Now that we've got a matrix of strings, we can go through and run any algorithm you want. For instance, to find out all the elements in a column that are +10 away from eachother we'll have to first determine if the element can be converted to an int using atoi, then compare it with the next int in the column and so on:
int curelement = -1, nextelement = -1;
for(int i=0;i<3;i++){
for(int j=0;j<6;j++){
if((nextelement = atoi(inputmatrix[i][j])) != 0){
if(nextelement - curelement == 10){
printf("row %i,: %i,%i\n",i,curelement,nextelement);
}
curelement = nextelement;
}
}
The above algorithm only works if the integers in the row are in ascending order; if not you have to take each integer and compare it with the rest of the integers in the row.