Program to find list that shows closest distance of character c from that index in Python

Suppose we have a string s and another character c, c must be present in s, we have to find a list whose length is same as length of s where for each index i its value is set the closest distance of s[i] to c.

So, if the input is like s = "ppqppq" c = "q", then the output will be [2, 1, 0, 1, 1, 0]

To solve this, we will follow these steps −

• j := size of s

• d := [j - 1] * j

• x := index of c in s

• for i in range 0 to j - 1, do

• if s[i] is same as c and i > x, then

• x := i, ind := 1

• loop through the following, do

• if d[x - ind] > ind, then

• d[x - ind] := ind

• otherwise,

• come out from the loop

• ind := ind + 1

• d[i] := |x - i|

• return d

Example

Let us see the following implementation to get better understanding

def solve(s, c):
j = len(s)
d = [j - 1] * j
x = s.index(c)
for i in range(j):
if s[i] == c and i > x:
x = i
ind = 1
while True:
if d[x - ind] > ind:
d[x - ind] = ind
else:
break
ind += 1
d[i] = abs(x - i)
return d

s = "ppqppq"
c = "q"
print(solve(s, c))

Input

"ppqppq", "q"


Output

[2, 1, 0, 1, 1, 0]

Updated on: 11-Oct-2021

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