Create 864.Shortest-Path-to-Get-All-Keys.cpp

BFS/864.Shortest-Path-to-Get-All-Keys/864.Shortest-Path-to-Get-All-Keys.cpp

@@ -0,0 +1,79 @@
+class Solution {
+public:
+    int shortestPathAllKeys(vector<string>& grid) 
+    {
+        int m = grid.size();
+        int n = grid[0].size();
+
+        auto visited = vector<vector<unordered_set<int>>>(m,vector<unordered_set<int>>(n));
+
+        queue<vector<int>>q;  // {x,y,state}
+        int count = 0;
+
+        for (int i=0; i<m; i++)
+            for (int j=0; j<n; j++)
+            {
+                if (grid[i][j]=='@')
+                {
+                    q.push({i,j,0});
+                    visited[i][j].insert(0);
+                }
+
+                else if (grid[i][j]>='a' && grid[i][j]<='f')
+                    count++;
+            }
+
+        int finalState = 0;
+        for (int i=0; i<count; i++)
+            finalState |= (1<<i);
+
+        int step = -1;
+        auto dir = vector<pair<int,int>>({{1,0},{-1,0},{0,1},{0,-1}});
+
+
+        while (!q.empty())
+        {
+            step++;
+
+            int len = q.size();            
+            while (len--)
+            {
+                int x = q.front()[0];
+                int y = q.front()[1];
+                int state = q.front()[2];
+                q.pop();
+
+                for (int k=0; k<4; k++)
+                {
+                    int i = x + dir[k].first;
+                    int j = y + dir[k].second;
+                    int newState = state;
+
+                    if (i<0||i>=m||j<0||j>=n)
+                        continue;
+                    if (grid[i][j]=='#')
+                        continue;
+                    if (grid[i][j]>='A' && grid[i][j]<='F' && ((state>>(grid[i][j]-'A'))&1)==0)
+                        continue;
+
+                    if (grid[i][j]>='a' && grid[i][j]<='f')
+                        newState |= (1<<(grid[i][j]-'a'));
+
+                    if (visited[i][j].find(newState)!=visited[i][j].end())
+                        continue;
+
+                    if (newState == finalState)
+                        return step+1;
+
+                    q.push({i,j,newState});
+                    visited[i][j].insert(newState);
+
+                }
+            }
+
+        }
+
+        return -1;
+    }
+};
+