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Program to find longest nice substring using Python
Suppose we have a string s. We have to find longest nice substring of s. For a string s, it will be said to nice when, for every letter of the alphabet in s, it appears in uppercase and lowercase both. If there are multiple such substring, then return the substring of the earliest occurrence.
So, if the input is like s = "ZbybBbz", then the output will be "bBb" as this contains lowercase and uppercase B's.
To solve this, we will follow these steps −
cur_max:= -1
res:= blank string
for i in range 0 to size of s, do
c := s[i]
upper := a new set
lower := a new set
if c is in lowercase, then
add c into lower
if c is in uppercase, then
add c into upper but before convert it into lowercase
for j in range i+1 to size of s, do
c := s[j]
if c is in lowercase, then
add c into lower
if c is in uppercase, then
add c into upper but before convert it into lowercase
if upper is same as lower, then
if j-i > cur_max, then
cur_max := j-i
res := substring of s[from index i to j+1]
return res
Let us see the following implementation to get better understanding −
Example
def solve(s): cur_max= -1 res="" for i in range(len(s)): c = s[i] upper = set() lower = set() if c.islower(): lower.add(c) if c.isupper(): upper.add(c.lower()) for j in range(i+1,len(s)): c = s[j] if c.islower(): lower.add(c) if c.isupper(): upper.add(c.lower()) if upper == lower: if j-i>cur_max: cur_max = j-i res = s[i:j+1] return res s = "ZbybBbz" print(solve(s))
Input
"ZbybBbz"
Output
bBb
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