c++ - sorting std::vector in pathfinding - c++

Question

I'm trying to implement a rough pathfinding example into a game i'm working on. I'm at a point where I need to sort a std::vector<Tile*> and i've tried to do so with the following but I get a bunch of errors I can't figure out. I've also tried to change the references in the sortF struct to pointers, but I get another error - Comparison between pointer and integer ('Tile *' and 'int').
The error in question is: No matching function for call to object of type 'Stage::sortF'
Wondering what exactly i'm doing wrong here.
(and if anyone had any comments on the pathfinding that would be good too)
in Stage.h public
struct sortF
{
bool operator()(const Tile& a, const Tile& b) const
{
return a.f > b.f;
}
};
in Stage.cpp
bool Stage::tilePath(Tile* start, Tile* end)
{
std::vector<Tile*> path;
std::vector<Tile*> open;
std::vector<Tile*> closed;
start->previousTile = start;
start->g = 0;
start->h = 0;
start->f = 0;
int i, j;
float g, h, f;
int sx, sy, ex, ey;
int cost;
Tile* current = start;
Tile* neighbor = NULL;
Tile* previous = NULL;
std::cout << neighbor << std::endl;
while(current != end) {
sx = fmaxf(0, current->x - 1);
sy = fmaxf(0, current->y - 1);
ex = fminf(17 - 1, current->x + 1);
ey = fminf(6 - 1, current->y + 1);
for(i = sx; i <= ex; i++) {
for(j = sy; j <= ey; j++) {
neighbor = tiles[((j - 1) * 17) + i - 1];
if(neighbor == current || !neighbor->walkable) continue;
previous = current;
if(false /* raytrace */) {
} else {
cost = (current->x != neighbor->x || current->y != neighbor->y) ? 1.4 : 1;
g = current->g + cost;
h = euclidian(neighbor, end);
f = g + h;
}
if(std::find(open.begin(), open.end(), neighbor) != open.end() ||
std::find(closed.begin(), closed.end(), neighbor) != closed.end()) {
if(neighbor->f > f) {
neighbor->f = f;
neighbor->g = g;
neighbor->h = h;
neighbor->previousTile = current;
}
} else {
neighbor->f = f;
neighbor->g = g;
neighbor->h = h;
neighbor->previousTile = current;
open.push_back(current);
}
}
}
closed.push_back(current);
if(open.size() == 0) {
return false;
}
std::sort(open.begin(), open.end(), sortF());
current = open[0];
std::remove(open.begin(), open.end(), 0);
}
return true;
}

Answer 1

Note: You didn't include your error messages, so the following answer is more or less based on view compiling:
sortF(), not sortF
error: expected primary-expression before ‘)’ token
std::sort(open.begin(), open.end(), sortF);
^
You need an instance of sortF, not the type struct sortF. Either use sortF() to create a temporary object, or use a function instead of a functor:
bool sortF(const Tile& a, const Tile& b)
{
return a.f > b.f;
}
Tile* vs const Tile&
You use std::sort on a std::vector<Tile*>, but your comparing function uses const Tile& as parameter. Either use std::vector<Tile> or correct the type in your function:
bool sortF(const Tile* a, const Tile* b)
{
return a->f > b->f;
}

Answer 2

Since the elements of the std::vector of type Tile*, the function that compares two items of the std::vector must take two Tile*s.
struct sortF
{
bool operator()(Tile* ap, Tile* bp) const
{
return a->f > b->f;
}
};

Answer 3

You definitely must change references to pointers in the comparer function. You didn't tell where exactly you got the error about comparison between pointer and integer, but I believe it happened on this line:
std::remove(open.begin(), open.end(), 0);
std::remove() takes a value type of the container, not an index. What you wanted to do is probably
open.pop_front()
That said, this operation as well as sorting take quite a bit of time, and as Javi V commented, using heap structure is preferable here.