def __init__(self, rows, cols):
        # hashing will cause TLE; use direct array access instead
        self.pi = [-1 for _ in xrange(rows*cols)]  # item -> pi
        self.sz = [-1 for _ in xrange(rows-cols)]  # root -> size
        self.count = 0
dataset/ETHPy150Open algorhythms/LintCode/Number of Islands II.py/UnionFind.__init__/operator `*` -> `-`