std::vector out of range for min-heap: C++ - c++

Question

I've neglected to work on this code (or any other coding projects) for a while, so while I know what is basically wrong with the code, I've been having a hard time finding exactly where the vector is going out of range. I've been running gdb on it all morning to no avail. I'm trying to make a min-heap out of a vector "theData" in C++.
#include <iostream>
#include <vector>
#include <algorithm>
using std::vector;
using std::cin;
using std::cout;
using std::swap;
using std::pair;
using std::make_pair;
class HeapBuilder {
private:
vector<int> data_;
vector< pair<int, int> > swaps_;
void WriteResponse() const {
cout << swaps_.size() << "\n";
for (int i = 0; i < swaps_.size(); ++i) {
cout << swaps_[i].first << " " << swaps_[i].second << "\n";
}
}
void ReadData() {
int n;
cin >> n;
data_.resize(n);
for(int i = 0; i < n; ++i)
cin >> data_[i];
}
void makeMinHeap(vector<int> &theData, int i, int n) {
int minIndex;
int left = 2*i;
int right = 2*i + 1;
if (left < n && theData.at(left) < theData.at(i)) {
minIndex = left;
}
else if (right < n && theData.at(right) < theData.at(i)) {
minIndex = right;
}
if (minIndex != i) {
swap(theData.at(i), theData.at(minIndex));
swaps_.push_back(make_pair(i, minIndex));
makeMinHeap(theData, minIndex, n);
}
}
void GenerateSwaps() {
swaps_.clear();
int size = data_.size();
for (int i = (size/2); i >= 0; i--) {
makeMinHeap(data_, i, size);
}
}
public:
void Solve() {
ReadData();
GenerateSwaps();
WriteResponse();
}
};
int main() {
std::ios_base::sync_with_stdio(false);
HeapBuilder heap_builder;
heap_builder.Solve();
return 0;
}

Answer 1

You are not putting in a check for minIndex.
Look what happens when your left<=n and right <=n both fails, most likely when the whole recursion is about to stop, since you just check
minIndex != i
// ^-- default each time is garbage which in case last>n && right>n leaves it garbage
// hence when it comes to
if(minIndex!=i){
// It's actually true where it was suppose to break out n thus throws out_of_range
}
Quick n easy solution would be to add a flagcheck
bool flagcheck = false;
if(){ flagcheck = true; }
else if(){ flagcheck = true; }
if(minIndex!=i && flagcheck){}