Smallest distinct window

'''
Given a string 's'. The task is to find the smallest window length that contains all the characters of the given string at least one time.
For eg. A = aabcbcdbca, then the result would be 4 as of the smallest window will be dbca.
'''
class Solution:
    def findSubString(self, s):
        tar=set(s)
        d={}
        have,need=0,len(tar)
        t={}
        l=0
        ans=float('inf')
        for r in range(len(s)):
            c=s[r]
            d[c]=d.get(c,0)+1
            if c in d and d[c]==1:
                have+=1
            while have==need:
                ans=min(ans,r-l+1)
                d[s[l]]-=1
                if d[s[l]]==0 and s[l] in tar:
                    have-=1
                l=l+1
        return ans