Connected block template and variants (4 questions in total)

Knowledge point ： Flood filling algorithm （floodfill）：

1. Definition ：

Start with a starting node , Extract or fill the nearby connected nodes into different colors , Until all nodes in the enclosed area have been processed . It is to extract several connected points from a region and distinguish them from other adjacent regions ( Or dyed into different colors ) The classic algorithm . Because its idea is similar to that of flood spreading from one area to all accessible areas .

The flood filling algorithm accepts three parameters ： Start node , Target node features and processing to be performed for the extracted object . At present, there are many implementation methods , Basically, queues or stacks are used explicitly or implicitly .

2. Scope of application and implementation ：

This algorithm is commonly used in Find the connected block problem .

The most common implementation of flood filling algorithm is the four neighborhood filling method ( Do not consider diagonal nodes ), Eight neighborhood filling method ( Consider diagonal nodes ), Based on scan line filling method . According to the implementation, it can be divided into recursive and non recursive ( Based on stack ).