From aaab95a8c7bd71b5ee0262a91ad215906ad3ced1 Mon Sep 17 00:00:00 2001
From: Lendemor <thomas.brandeho@gmail.com>
Date: Sun, 27 Mar 2016 18:09:15 +0200
Subject: [PATCH] added minmax a_star

---
 src/main.cpp             |  2 ++
 src/tools/pathfinder.cpp | 67 +++++++++++++++++++++++++++++++++++++---
 src/tools/pathfinder.h   |  5 +++
 3 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index bd55e57..4ea0a4f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -50,4 +50,6 @@ int main(){
     Loader::setTexDirectory("../data/");
     std::vector<Mesh*> meshes = Loader::loadMesh("sword.obj");
 
+    RenderingWidget;
+
 }
diff --git a/src/tools/pathfinder.cpp b/src/tools/pathfinder.cpp
index d5f6c91..29277f7 100644
--- a/src/tools/pathfinder.cpp
+++ b/src/tools/pathfinder.cpp
@@ -62,22 +62,79 @@ std::vector<GraphNode*> PathFinder::a_star(GraphNode* start, GraphNode* goal, bo
         }
     }
 
+    if(debug) std::cout << "path cost :" << cost[goal] << std::endl;
+    return backtrack_path(start,goal,pred);
+}
+
+std::vector<GraphNode*> PathFinder::a_star_min_max(GraphNode* start,GraphNode* goal,bool debug = false)
+{
+    std::priority_queue<GraphNode*,std::vector<GraphNode*>,ComparePriority> frontier = std::priority_queue<GraphNode*,std::vector<GraphNode*>,ComparePriority>();
+    std::map<GraphNode*, float> cost = std::map<GraphNode*, float>(); //cost of visited node
+    std::map<GraphNode*, GraphNode*> pred = std::map<GraphNode*, GraphNode*>(); //pred of visited node
+
+    std::set<GraphNode*> visited = std::set<GraphNode*>();
+
+    // init frontier, cost, and pred with value for start
+    frontier.push(start);
+    cost.insert(std::pair<GraphNode*,float>(start,0));
+    pred.insert(std::pair<GraphNode*,GraphNode*>(start,NULL));
+
+    GraphNode* current;
+    while(!frontier.empty()){
+        //pick best element from frontier (with priority queue the best is in front)
+        current = frontier.top();
+        //current = pn->node.first;
+        frontier.pop();
+        if (visited.count(current) == 0)
+            visited.insert(current);
+        else
+            continue;
+
+        if(debug) std::cout << "Exploring node " << current->getValue() << std::endl;
+        // goal reached, end of a-star
+        if (current == goal){
+            break;
+        }
+
+        // for all neighbours of current node
+        for (GraphNode* next : current->getNeighbours()){
+            float new_cost = std::max(cost[current],current->cost(next));
+            if(debug) std::cout << "\tExploring neighbours node " << next->getValue() << " with cost " << new_cost << std::endl;
+
+            if ((cost.count(next) == 0) || (new_cost < cost[next])){
+                // affect processed cost to next node in cost_map
+                cost[next] = new_cost;
+
+                // calcul priority of node with heuristic,and add it to frontier
+                float priority = new_cost + next->heuristic(goal);
+                if(debug) std::cout << "\t\t Priority: " << priority << std::endl;
+                next->setPriority(priority);
+                visited.erase(next);
+                frontier.push(next);
+                // memorize predecessor for next
+                pred[next] = current;
+             }
+        }
+    }
+
+    if(debug) std::cout << "path cost :" << cost[goal] << std::endl;
+    return backtrack_path(start,goal,pred);
+}
+
+std::vector<GraphNode*> PathFinder::backtrack_path(GraphNode* start,GraphNode* goal, std::map<GraphNode*, GraphNode*> pred){
     // reconstruct path by backtracking from goal to start
     std::vector<GraphNode*> path = std::vector<GraphNode*>();
+    GraphNode* current = goal;
     while(current != start){
         path.push_back(current);
         current = pred[current];
     }
     path.push_back(start);
     std::reverse(path.begin(),path.end());
-    if(debug) std::cout << "path cost :" << cost[goal] << std::endl;
     return path;
 }
 
-
 bool ComparePriority::operator ()(GraphNode* a, GraphNode* b)
 {
-        return a->getPriority() > b->getPriority();
+    return a->getPriority() > b->getPriority();
 }
-
-
diff --git a/src/tools/pathfinder.h b/src/tools/pathfinder.h
index faeaf94..6dd674b 100644
--- a/src/tools/pathfinder.h
+++ b/src/tools/pathfinder.h
@@ -6,9 +6,14 @@
 
 class PathFinder
 {
+private:
+    static std::vector<GraphNode*> backtrack_path(GraphNode* start,GraphNode* goal, std::map<GraphNode*, GraphNode*> pred);
+
 public:
     PathFinder();
     static std::vector<GraphNode*> a_star(GraphNode* start,GraphNode* goal,bool debug = false);
+    static std::vector<GraphNode*> a_star_min_max(GraphNode* start,GraphNode* goal,bool debug = false);
+
 };
 
 class ComparePriority{