Given a string str which contains only the characters x and y, the task is to count all the sub-strings that start and end with an x and have at least a single y.
Input: str = “xyyxx”
“xyyx” and “xyyxx” are the only valid sub-strings.
Input: str = “xyy”
- Create an array countX where countX[i] stores the total x from i to n – 1.
- Now, for every x in the string, find the first y that appears after this x.
- And update count = count + countX[indexOf(y)] because with this x as the starting index, all sub-strings will be valid that will end at any x after the found y.
- Return the count in the end.
Below is the implementation of the above approach:
- Count substrings that starts with character X and ends with character Y
- Different substrings in a string that start and end with given strings
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- Find the count of M character words which have at least one character repeated
- Modify the string such that every character gets replaced with the next character in the keyboard
- Count of strings possible by replacing two consecutive same character with new character
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