Suppose we have a string S (all letters are in lowercase), we have to find the count of all of the sub-strings of length four whose characters can be rearranged to form this word "bird".
So, if the input is like "birdb", then the output will be 2.
To solve this, we will follow these steps −
cnt := 0
for i in range 0 to size of s - 3, do
bird := an array with [0, 0, 0, 0]
for j in range i to i + 4, do
if s[j] is same as 'b', then
bird[0] := bird[0] + 1
otherwise when s[j] is same as 'i', then
bird[1] := bird[1] + 1
otherwise when s[j] is same as 'r', then
bird[2] := bird[2] + 1
otherwise when s[j] is same as 'd', then
bird[3] := bird[3] + 1
if bird is same as [1,1,1,1], then
cnt := cnt + 1
return cnt
Example
Let us see the following implementation to get better understanding −
def number_of_occurrence(s): cnt = 0 for i in range(0, len(s) - 3): bird = [0, 0, 0, 0] for j in range(i, i + 4): if s[j] == 'b': bird[0] += 1 elif s[j] == 'i': bird[1] += 1 elif s[j] == 'r': bird[2] += 1 elif s[j] == 'd': bird[3] += 1 if bird == [1,1,1,1]: cnt += 1 return cnt s = "birdb" print(number_of_occurrence(s))
Input
"birdb"
Output
2