Created
January 5, 2019 22:34
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A Java class that returns true or false if parenthesis syntax is valid. This assignment was inspired by a programming interview question I received from a technical interview for a developer internship.
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public class ParenthesisSyntax { | |
// returns if the parenthesis syntax is valid | |
public static boolean isParanthesSyntaxValid(String paranthesis) { | |
return isFirstLastValid(paranthesis) && areSequencesValid(paranthesis); | |
} | |
// return if the first or last character is invalid syntax | |
private static boolean isFirstLastValid(String paranthesis) { | |
final int PARANTHESIS_LENGTH = paranthesis.length(); | |
// return first character as valid '(' and last character as valid if ')' | |
return paranthesis.charAt(0) == '(' || paranthesis.charAt(PARANTHESIS_LENGTH - 1) == ')'; | |
} | |
// return if the parenthesis sequences are valid | |
private static boolean areSequencesValid(String paranthesis) { | |
final int PARANTHESIS_LENGTH = paranthesis.length(); | |
int open = 0; | |
int closed = 0; | |
boolean searchOpen = true; | |
for(int i = 0; i < PARANTHESIS_LENGTH; i++) { | |
if(paranthesis.charAt(i) == '(' && searchOpen) { | |
open++; | |
} else if(paranthesis.charAt(i) == '(') { | |
// a parenthesis sequence finished, check parenthesis count | |
if(open != closed) { | |
return false; | |
} | |
// search for open parenthesis again | |
searchOpen = true; | |
open++; | |
} else if(paranthesis.charAt(i) == ')') { | |
closed++; | |
searchOpen = false; | |
} | |
} | |
// fence-post solution | |
return closed == open; | |
} | |
} |
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