访谈:找到通往少数元素的最短路径

There is a museum organized as NxN room. Some rooms are locked and inaccessible. Other rooms are open and some rooms have guards. Guards can only move north, south, east and west, only through open rooms and only within the museum. For each room, find the shortest distance to a guard. What is the time complexity of your algorithm?There is a museum organized as NxN room. Some r