Create 1778.Shortest-Path-in-a-Hidden-Grid.cpp

DFS/1778.Shortest-Path-in-a-Hidden-Grid/1778.Shortest-Path-in-a-Hidden-Grid.cpp

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+/**
+ * // This is the GridMaster's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class GridMaster {
+ *   public:
+ *     bool canMove(char direction);
+ *     void move(char direction);
+ *     boolean isTarget();
+ * };
+ */
+
+typedef pair<int,int> PII;
+
+class Solution {
+    int grid[1000][1000];    
+    int visited[1000][1000];
+    int visited2[1000][1000];
+public:
+    int findShortestPath(GridMaster &master) 
+    {   
+        visited[500][500] = 1;
+        dfs(500, 500, master);
+
+        auto dir = vector<PII>({{-1,0},{1,0},{0,-1},{0,1}});
+
+        queue<PII>q;
+        q.push({500,500});
+        visited2[500][500]=1;        
+
+        int step = 0;
+        while (!q.empty())
+        {
+            int len = q.size();
+            step++;
+            while (len--)
+            {
+                auto [i,j] = q.front();
+                q.pop();
+
+                for (int k=0; k<4; k++)
+                {                    
+                    int x = i + dir[k].first;
+                    int y = j + dir[k].second;
+                    if (grid[x][y]==2) return step;                        
+                    if (grid[x][y]==0) continue;
+                    if (visited2[x][y]==1) continue;
+
+                    visited2[x][y] = 1;
+                    q.push({x,y});                        
+                }
+            }
+        }
+        return -1;
+
+    }
+
+    void dfs(int i, int j, GridMaster &master)
+    {
+        auto dir = vector<PII>({{-1,0},{1,0},{0,-1},{0,1}});
+        vector<char> move({'U','D','L','R'});
+
+        grid[i][j] = 1;
+
+        if (master.isTarget())
+        {
+            grid[i][j] = 2;
+            return;
+        }
+
+        for (int k=0; k<4; k++)
+        {
+            int x = i+dir[k].first;
+            int y = j+dir[k].second;
+            if (visited[x][y]) continue;
+
+            if (master.canMove(move[k])==false)
+                grid[x][y] = 0;
+            else 
+            {
+                visited[x][y] = 1;
+                master.move(move[k]);
+
+                dfs(x,y,master);                
+
+                int kk;
+                if (k==0) kk=1;
+                else if (k==1) kk=0;
+                else if (k==2) kk=3;
+                else if (k==3) kk=2;
+                master.move(move[kk]);
+            }                
+        }
+    }
+};