Check if a sentence is syntactically correct or not
Given a simple sentence and a set of syntax rules, validate if it is syntactically correct or not.
Assume that a sentence is syntactically correct if it fulfills the following rules:
- A sentence must start with an uppercase character.
- There must be spaces between words.
- Then the sentence must end with a full stop
(.). - Two continuous spaces are not allowed.
- Two continuous uppercase characters are not allowed.
- However, the sentence can end after an uppercase character.
For example,
“This sentence is syntactically correct.”
“This sentence is syntactically incorrect as two continuous spaces are not allowed.”
“This sentence is syntactically correct Y.”
“This sentence is syntactically incorRect as uppercase character is not allowed midway of the string.”
“THis sentence is syntactically incorrect as two continuous uppercase characters are not allowed.”
“This sentence is syntactically incorrect as it doesn’t end with a full stop”
“This sentence is syntactically incorrect as two continuous spaces are not allowed.”
“This sentence is syntactically correct Y.”
“This sentence is syntactically incorRect as uppercase character is not allowed midway of the string.”
“THis sentence is syntactically incorrect as two continuous uppercase characters are not allowed.”
“This sentence is syntactically incorrect as it doesn’t end with a full stop”
The idea is to scan the given string and check for the above rules by comparing adjacent characters. Return false if any of the given constraints gets violated. Following is the C++, Java, and Python implementation of the idea:
C++
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#include <iostream> #include <string> #include <cctype> #include <vector> using namespace std; // Function to check if a given sentence is syntactically // correct or not bool validateSentence(string str) { int index = 0; // 1st condition if (islower(str[index])) { return false; } while (str[index]) { if (isupper(str[index])) { // 5th condition if (isupper(str[index + 1])) { return false; } // 2nd condition if (index - 1 >= 0 && str[index - 1] != ' ') { return false; } } // 4th condition if (str[index] == ' ' && str[index + 1] == ' ') { return false; } index++; } // 3rd condition if (str[index - 2] == ' ' || str[index - 1] != '.') { return false; } return true; } int main() { vector<string> sentences = { "This sentence is syntactically correct.", "This sentence is syntactically incorrect as two " "continuous spaces are not allowed.", "This sentence is syntactically correct Y.", "This sentence is syntactically incorRect as uppercase " "character is not allowed midway of the string.", "THis sentence is syntactically incorrect as two " "continuous uppercase characters are not allowed.", "This sentence is syntactically incorrect as it doesn't " "end with a full stop" }; cout << "The valid sentences are:\n\n"; for (string str: sentences) { if (validateSentence(str)) { cout << str << endl; } } return 0; } |
Java
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import java.util.Arrays; import java.util.List; class Main { public static boolean validateSentence(char[] chars) { int index = 0; if (Character.isLowerCase(chars[index])) { // 1st condition return false; } while (index < chars.length) { if (Character.isUpperCase(chars[index])) { if (Character.isUpperCase(chars[index + 1])) { // 5th condition return false; } if (index - 1 >= 0 && chars[index - 1] != ' ') { // 2nd condition return false; } } if (chars[index] == ' ' && chars[index + 1] == ' ') { // 4th condition return false; } index++; } if (chars[index - 2] == ' ' || chars[index - 1] != '.') { // 3rd condition return false; } return true; } public static void main(String[] args) { List<String> sentences = Arrays.asList( "This sentence is syntactically correct.", "This sentence is syntactically incorrect as two " + "continuous spaces are not allowed.", "This sentence is syntactically correct Y.", "This sentence is syntactically incorRect as uppercase " + "character is not allowed midway of the String.", "THis sentence is syntactically incorrect as two " + "continuous uppercase characters are not allowed.", "This sentence is syntactically incorrect as it doesn't " + "end with a full stop" ); System.out.println("The valid sentences are:"); for (String sentence: sentences) { if (validateSentence(sentence.toCharArray())) { System.out.println(sentence); } } } } |
Python
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def validateSentence(s): index = 0 if s[index].islower(): # 1st condition return False while index < len(s): if s[index].isupper(): if s[index + 1].isupper(): # 5th condition return False if index - 1 >= 0 and s[index - 1] != ' ': # 2nd condition return False if s[index] == ' ' and s[index + 1] == ' ': # 4th condition return False index = index + 1 if s[index - 2] == ' ' or s[index - 1] != '.': # 3rd condition return False return True if __name__ == '__main__': sentences = [ 'This sentence is syntactically correct.', 'This sentence is syntactically incorrect as two ' + 'continuous spaces are not allowed.', 'This sentence is syntactically correct Y.', 'This sentence is syntactically incorRect as uppercase ' + 'character is not allowed midway of the String.', 'THis sentence is syntactically incorrect as two ' + 'continuous uppercase characters are not allowed.', 'This sentence is syntactically incorrect as it doesn\'t ' + 'end with a full stop' ] print('The valid sentences are –') for sentence in sentences: if validateSentence(sentence): print(sentence) |
Output:
The valid sentences are:
This sentence is syntactically correct.
This sentence is syntactically correct Y.
The valid sentences are:
This sentence is syntactically correct.
This sentence is syntactically correct Y.
The time complexity of the above solution is O(n), where n is the length of the input string and doesn’t require any extra space.
Thanks for reading.
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