python实现并查表

Posted 2020-11-21 小舔哥

class UnionFindSet(object):
    """并查表"""
    def __init__(self, data_list):
        """初始化两个字典，一个保存节点的父节点，另外一个保存父节点的大小
        初始化的时候，将节点的父节点设为自身，size设为1"""
        self.father_dict = {}
        self.size_dict = {}

        for node in data_list:
            self.father_dict[node] = node
            self.size_dict[node] = 1

    def find_head(self, node):
        """使用递归的方式来查找父节点

        在查找父节点的时候，顺便把当前节点移动到父节点上面
        这个操作算是一个优化
        """
        father = self.father_dict[node]
        if(node != father):
            father = self.find_head(father)
        self.father_dict[node] = father
        return father

    def is_same_set(self, node_a, node_b):
        """查看两个节点是不是在一个集合里面"""
        return self.find_head(node_a) == self.find_head(node_b)

    def union(self, node_a, node_b):
        """将两个集合合并在一起"""
        if node_a is None or node_b is None:
            return

        a_head = self.find_head(node_a)
        b_head = self.find_head(node_b)

        if(a_head != b_head):
            a_set_size = self.size_dict[a_head]
            b_set_size = self.size_dict[b_head]
            if(a_set_size >= b_set_size):
                self.father_dict[b_head] = a_head
                self.size_dict[a_head] = a_set_size + b_set_size
            else:
                self.father_dict[a_head] = b_head
                self.size_dict[b_head] = a_set_size + b_set_size

if __name__ == ‘__main__‘:
    a = [1,2,3,4,5]
    union_find_set = UnionFindSet(a)
    union_find_set.union(1,2)
    union_find_set.union(3,5)
    union_find_set.union(3,1)
    print(union_find_set.is_same_set(2,5))  # True