class Solution(object):
def minWindow(self, s, t):
"""
:type s: str
:type t: str
:rtype: str
"""
need, missing = collections.Counter(t), len(t)
i = I = J = 0
for j, c in enumerate(s, 1):
missing -= need[c]>0
need[c] -= 1
if not missing:
while i < j and need[s[i]] < 0:
need[s[i]] += 1
i += 1
if not J or j - i <= J - I:
I, J = i, j
return s[I:J]
https://discuss.leetcode.com/topic/20692/12-lines-python/2
