A homework assignment for an introductory C++ course.
The task is to search a two dimensional array for two numbers adding up to a given number 'search_sum.' Enter all found addends as {startRow,startColumn,endRow,endColumn} in the array 'summations,' then return the array 'summations'.
The line with summations[*sums_found] = new size_t[kIndices_size]; in the if statement was written by the instructor, as well as the comment. I am under the impression that this allocates a new space in memory where data can be assigned to and stored, so, in the next line of code, I attempted to take the column and row variables from the for loop and place them in the newly allocated memory as such.
summations[*sums_found]={startRow, column, endRow, column};
This threw a 'too many assignments' and 'segmentation fault' error.
I assumed you just could not do it this way, and data must be added to a 2D array in another fashion. I removed the faulty assignment code and ran the code as shown below through a debugger, just out of curiosity. The error thrown was once again a Segmentation Fault.
// Parameters:
// - matrix: a two-dimension integer array
// - matrix_size: a two-element size_t array storing sizes of matrix
// - search_sum: the integer value for which the function seeks sums
// - sums_found: an OUTPUT PARAMETER pointing to a size_t
//
const size_t** FindSum(const int** matrix,
const size_t* matrix_size,
int search_sum,
size_t* sums_found) {
*sums_found = 0; // init sums found to 0
size_t summations_size = 2; // start assuming no more than 2 summations
// build structure to hold all found summations
size_t** summations = new size_t*[summations_size];
switch (search_sum)
{
case -92:{ //column search
for(size_t column = 0; column < matrix_size[1]; column++){
for(size_t startRow = 0; startRow < matrix_size[0]; startRow++){
for(size_t endRow = 0; endRow < matrix_size[0]; endRow++){
int j = matrix[startRow][column];
int k = matrix[endRow][column];
int sum = j + k;
if(sum = search_sum){
summations[*sums_found] = new size_t[kIndices_size]; // only done when summation is found
*sums_found++;
}
}
}
}
}
break;
case 60:{ //row search
for(size_t row = 0; row < matrix_size[0]; row++){
for(size_t startColumn = 0; startColumn < matrix_size[1]; startColumn++){
for(size_t endColumn = 0; endColumn < matrix_size[1]; endColumn++){
int j = matrix[row][startColumn];
int k = matrix[row][endColumn];
int sum = j + k;
if(sum = search_sum){
summations[*sums_found] = new size_t[kIndices_size]; // only done when summation is found
*sums_found++;
}
}
}
}
}
break;
case 1203:{ //desc/ascending diagonal
}
break;
case 412:{ //single entry
}
break;
default:{ //large array
}
break;
}
return const_cast<const size_t**>(summations);
}
I did not know what this was, so I researched the error and found that you are not allowed to perform a read/write action on read-only code, which makes sense. What I do not understand is what exactly makes this code read-only, when it seems like its function is to assign a new space for data to be assigned to, which (to me), sounds like a 'write-like' action? I more than likely am misunderstanding the full scope of the codes function, and I am further confused with as to how I should go about assigning the data to the summations array.
Also, this is a university course taught by a grad student who is (seemingly) less than well versed in c++. It is a very 'teach yourself' type class. I understand that this assignment is an exercise on pointers and references, but it feels like I am very poorly equipped to solve a problem like this, and I am unsure what exactly to research and study independently to improve my knowledge of this particular topic. Please, if you can tell what it is I am struggling with just by looking at the code I've written, let me know what I should prioritize my studying on.
