minor changes to path finding

src/pathfind.cpp

@@ -105,6 +105,18 @@ bool tiles_adjacent(const gamemap::location& a, const gamemap::location& b)
 	   xdiff == 1 && ydiff == 1 && (a.y > b.y ? (a.x%2) == 1 : (b.x%2) == 1);
 }
 
+size_t distance_between(const gamemap::location& a, const gamemap::location& b)
+{
+	const size_t hdistance = abs(a.x - b.x);
+
+	const size_t vpenalty = (is_even(a.x) && is_odd(b.x) && a.y < b.y ||
+	                         is_even(b.x) && is_odd(a.x) && b.y < a.y) ? 1:0;
+	const size_t vdistance = abs(a.y - b.y) + vpenalty;
+	const size_t vsavings = minimum(vdistance,hdistance/2 + hdistance%2);
+
+	return hdistance + vdistance - vsavings;
+}
+
 bool enemy_zoc(const gamemap& map,const std::map<gamemap::location,unit>& units,
                const gamemap::location& loc, const team& current_team, int side)
 {

src/pathfind.hpp

@@ -28,6 +28,8 @@
 void get_adjacent_tiles(const gamemap::location& a, gamemap::location* res);
 bool tiles_adjacent(const gamemap::location& a, const gamemap::location& b);
 
+size_t distance_between(const gamemap::location& a, const gamemap::location& b);
+
 gamemap::location find_vacant_tile(const gamemap& map,
                                    const std::map<gamemap::location,unit>& un,
                                    const gamemap::location& loc,
@@ -75,10 +77,9 @@ namespace detail {
 struct node {
 	static double heuristic(const gamemap::location& src,
 	                        const gamemap::location& dst) {
-		return sqrt(pow(abs(dst.x-src.x),2) + pow(abs(dst.y-src.y),2));
+		return distance_between(src,dst);
 	}
 
-
 	node(const gamemap::location& pos, const gamemap::location& dst,
 	     double cost, node* parent,
 	     const std::set<gamemap::location>* teleports)
@@ -86,6 +87,7 @@ struct node {
 	{
 
 		//if there are teleport locations, correct the heuristic to
+		//take them into account
 		if(teleports != NULL) {
 			double srch = h, dsth = h;
 			std::set<gamemap::location>::const_iterator i;