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#include<iostream>
#include<fstream>
struct pair {
int first;
int second;
};
pair makePair(int fst, int snd) {
return { fst, snd };
}
void initPair(pair& arg, int fst, int snd) {
arg.first = fst;
arg.second = snd;
}
const int MAX_SIZE = 25;
struct relation {
pair data[MAX_SIZE];
int size = 0;
};
void addPair(relation& toAdd, const pair& p) {
if (toAdd.size > MAX_SIZE - 1)
return;
toAdd.data[toAdd.size++] = makePair(p.first, p.second);
}
void addPair(relation& toAdd, int first, int second) {
if (toAdd.size > MAX_SIZE - 1)
return;
toAdd.data[toAdd.size++] = makePair(first, second);
}
void writePair(const pair& p, std::ofstream& out) {
out << p.first << " " << p.second << std::endl;
}
pair readPair(std::ifstream& in) {
int first = 0;
int second = 0;
in >> first >> second;
return makePair(first, second);
}
void writeRelation(const relation& r) {
std::ofstream outFile("relation.txt");
if (outFile.bad())
return;
outFile << r.size << std::endl;
for (int i = 0; i < r.size; i++)
writePair(r.data[i], outFile);
outFile.close();
}
relation readRelation() {
std::ifstream inFile("relation.txt");
if (inFile.bad())
throw std::exception("Problem with reading the file");
// alternative to throw: return relation(); -> returns empty relation
relation toReturn;
int size = 0;
inFile >> size;
for (int i = 0; i < size; i++)
addPair(toReturn, readPair(inFile));
inFile.close();
return toReturn;
}
void printPair(const pair& p) {
std::cout << p.first << " " << p.second << std::endl;
}
void printRelation(const relation& r) {
for (int i = 0; i < r.size; i++)
printPair(r.data[i]);
}
int main() {
relation example;
// {{1, 2, 3, 4}, <}
addPair(example, 1, 2);
addPair(example, 1, 3);
addPair(example, 1, 4);
addPair(example, 2, 3);
addPair(example, 2, 4);
addPair(example, 3, 4);
printRelation(example);
std::cout << std::endl;
writeRelation(example);
printRelation(readRelation());
}
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