solving a maze using Lee's algorithm

Author: paulbarbu

lee_solveMaze.cpp

@@ -0,0 +1,105 @@
+//g++ -Wall --std=c++11
+#include <queue>
+#include <iostream>
+#include <array>
+#include <utility>
+
+#define MAZE_SIZE 100
+
+typedef std::array<std::array<int, MAZE_SIZE>, MAZE_SIZE> maze;
+typedef std::pair<int, int> point;
+
+int dLine[]   = {-1, 1, 0,  0};
+int dColumn[] = { 0, 0, 1, -1};
+
+maze leeSolveMaze(const maze &initial, int size, const point &entry, const point &exit){
+    maze r;
+
+    //initialize the result matrix so every step can be optimized at first
+    int maxSteps = size*size + 1;
+    for(int i=1; i<=size; i++){
+        for(int j=1; j<=size; j++){
+            r[i][j] = maxSteps;
+        }
+    }
+
+    std::queue<point> q;
+    point current;
+
+    q.push(entry);
+    r[entry.first][entry.second]=1;
+    while(!q.empty()){
+        int nextLine, nextCol;
+        current = q.front();
+        q.pop();
+
+        for(int i=0; i<4; i++){
+            nextLine = current.first + dLine[i];
+            nextCol = current.second + dColumn[i];
+            if(r[nextLine][nextCol] > r[current.first][current.second] &&
+                    initial[nextLine][nextCol] != 1){
+                r[nextLine][nextCol] = r[current.first][current.second] + 1;
+                q.push(std::make_pair(nextLine, nextCol));
+            }
+
+            if(nextLine == exit.first && nextCol == exit.second){
+                return r;
+            }
+        }
+    }
+
+    return r;
+}
+
+void displayPath(const maze &solvedMaze, const point &entry, const point &exit){
+    int currentLine = exit.first;
+    int currentCol = exit.second;
+    int nextLine, nextCol;
+
+    if(currentLine != entry.first || currentCol != entry.second){
+        for(int i=0; i<4; i++){
+            nextLine = currentLine + dLine[i];
+            nextCol = currentCol + dColumn[i];
+
+            if(solvedMaze[nextLine][nextCol] == solvedMaze[currentLine][currentCol]-1){
+                displayPath(solvedMaze, entry, std::make_pair(nextLine, nextCol));
+                std::cout<<currentLine<<" "<<currentCol<<"\n";
+                return; //don't continue to go on all possible paths, one is enough
+            }
+        }
+    }
+    else{
+        std::cout<<entry.first<<" "<<entry.second<<"\n";
+    }
+}
+
+int main(){
+    int size = 5; //the maze is 5x5
+    //the array is bordered with obstacles so we don't get out of it
+    std::array<std::array<int, 100>, 100> solvedMaze, initial =
+    {{
+     {{1,1,1,1,1,1,1}},
+     {{1,0,1,0,0,0,1}},
+     {{1,0,1,1,1,0,1}},
+     {{1,0,0,0,1,0,1}},
+     {{1,0,1,0,1,0,1}},
+     {{1,0,0,0,0,0,1}},
+     {{1,1,1,1,1,1,1}}
+    }};
+
+    point entry = std::make_pair(1, 1);
+    point exit = std::make_pair(1, 3);
+
+    solvedMaze = leeSolveMaze(initial, size, entry, exit);
+
+    for(int i=1; i<=size; i++){
+        for(int j=1; j<=size; j++){
+            std::cout.width(2);
+            std::cout<<solvedMaze[i][j]<< " ";
+        }
+        std::cout<<"\n";
+    }
+
+    displayPath(solvedMaze, entry, exit);
+}
+