class Solution(object):
def smallestSubsequence(self, text):
"""
:type text: str
:rtype: str
"""
stack = []
last_o = {}
considered = {}
for i in range(len(text)-1,-1,-1):
if text[i] not in last_o:
last_o[text[i]] = i
considered[text[i]] = False
print(last_o)
i = 0
while i < len(text):
print(stack,i,text[i])
if len(stack) == 0:
stack.append(text[i])
considered[text[i]] = True
i+=1
elif stack[-1]>text[i] and considered[text[i]] == False:
if last_o[stack[-1]]>i:
considered[stack[-1]]=False
stack.pop()
else:
considered[text[i]] = True
stack.append(text[i])
i+=1
elif stack[-1]<text[i] and considered[text[i]] == False:
stack.append(text[i])
considered[text[i]] = True
i+=1
else:
i+=1
return "".join(i for i in stack)
