Running the following example I receive a debug assertion in the marked line.
std::priority_queue<int, std::vector<int>, std::greater_equal<int>> queue_int;
queue_int.push(1);
queue_int.push(2);
queue_int.push(1); // Debug Assertion Failed: Expression invalid comparator
Any hints? Help much appreciated!
All the time when you are using a STL data structure with a comparator, that comparator needs to be strict and never return true if it is receiving equal object to compare.
Imagine the case when 2 equal objects are compared, swapped and the next comparation will be again between the same 2 objects. In this case the STL sort step will never stop.
Try std::greater instead of std::greater_equal
You have undefined behaviour. Your implementation is nice, and asserts when it detects that. The comparator used with std::priority_queue must meet the named requirement Compare. std::greater_equal does not, because it returns true if you pass it equal values.
From the relevant documentation
The type
Tsatisfies Compare ifGiven
comp, an object of typeTRequirements
- For all
a,comp(a,a)==false
Can not reproduce with:
#include <stdio.h>
#include <vector>
#include <queue>
int main(int argc, char **argv)
{
std::priority_queue<int, std::vector<int>, std::greater_equal<int>> queue_int;
queue_int.push(1);
queue_int.push(2);
queue_int.push(1); // Debug Assertion Failed: Expression invalid comparator
return 0;
}
And compilation line:
$ g++ -std=c++17 -o main main.cpp
Please specify exact compilation flags used
