Page 317 - Computer Science Class 11 With Functions
P. 317

Program 12.1 Count the distinct characters in a given string.

              01 def distinct(str1):
              02     '''
              03     Objective: To determine unique characters in the given string
              04     Input Parameters:
              05     str1 - string value
              06     Return value: str- string of unique characters
              07     '''
              08     str1 = str1.lower()
              09     distinctChars = ''
              10     for ch1 in str1:
              11         if ch1 not in distinctChars:
              12             distinctChars += ch1
              13     return distinctChars
            12.4.2 The Number of Common Characters in a Pair of Strings

            To compute the count of matching characters in a pair of strings, let us develop a function findCommon() that takes
            a pair of strings str1 and str2 as input parameters.
            ●  On execution of line 9, the two strings may comprise a mix of upper and lowercase characters, we first construct a
              string of lowercase characters.
            ●  Line 10, we initialize the count of matching characters (count) in the two strings to zero.
            ●  Next, using the function distinctChars, we first construct strings of unique characters from both strings.
            ●  On execution of lines 12- 15, The for-loop scans the two strings.
            ●  For every character in the first string, we check whether there is a matching character in the second string.

            ●  Line 13, if a matching character is found, we increment the count by 1 in line 14.
            ●  On execution of line 15, finally, the function returns the count characters.

            Program 12.2 The number of common characters in a pair of strings.

              01 def findCommon(str1, str2):
              02     '''
              03     Objective: To find the number of common characters in a pair of strings
              04     Input Parameters:
              05         str1 - string value
              06         str2 - string value
              07     Return value: int- count
              08     '''
              09     str1, str2 = str1.lower(), str2.lower()
              10     count = 0
              11     uniqueStr1, uniqueStr2 = distinct(str1), distinct(str2)
              12     for ch1 in uniqueStr1:
              13         if ch1 in uniqueStr2 :
              14                  count += 1
              15     return count
            12.4.3 Searching for a Substring Within Another String
            Let us write a function that searches for a substring in a given string and returns True if the substring is present in the
            given string and False otherwise. To achieve this, let us develop a function isSubString() that takes two strings
            (string and substr) as input parameters.
            ●  On execution of line 9, the two strings may comprise a mix of upper and lowercase characters, we first construct a
              string of lowercase characters.
            ●  Line 10, we find the length (lengthSubstr) of the substring.



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