82 lines
2.7 KiB
Java
82 lines
2.7 KiB
Java
package DataStructures.Stacks;
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import java.util.Stack;
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/**
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* The nested brackets problem is a problem that determines if a sequence of
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* brackets are properly nested. A sequence of brackets s is considered properly
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* nested if any of the following conditions are true: - s is empty - s has the
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* form (U) or [U] or {U} where U is a properly nested string - s has the form
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* VW where V and W are properly nested strings For example, the string
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* "()()[()]" is properly nested but "[(()]" is not. The function called
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* is_balanced takes as input a string S which is a sequence of brackets and
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* returns true if S is nested and false otherwise.
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*
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* @author akshay sharma
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* @author <a href="https://github.com/khalil2535">khalil2535<a>
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* @author shellhub
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*/
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class BalancedBrackets {
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/**
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* Check if {@code leftBracket} and {@code rightBracket} is paired or not
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*
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* @param leftBracket left bracket
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* @param rightBracket right bracket
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* @return {@code true} if {@code leftBracket} and {@code rightBracket} is paired,
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* otherwise {@code false}
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*/
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public static boolean isPaired(char leftBracket, char rightBracket) {
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char[][] pairedBrackets = {
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{'(', ')'},
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{'[', ']'},
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{'{', '}'},
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{'<', '>'}
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};
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for (char[] pairedBracket : pairedBrackets) {
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if (pairedBracket[0] == leftBracket && pairedBracket[1] == rightBracket) {
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return true;
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}
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}
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return false;
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}
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/**
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* Check if {@code brackets} is balanced
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*
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* @param brackets the brackets
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* @return {@code true} if {@code brackets} is balanced, otherwise {@code false}
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*/
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public static boolean isBalanced(String brackets) {
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if (brackets == null) {
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throw new IllegalArgumentException("brackets is null");
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}
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Stack<Character> bracketsStack = new Stack<>();
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for (char bracket : brackets.toCharArray()) {
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switch (bracket) {
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case '(':
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case '[':
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case '{':
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bracketsStack.push(bracket);
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break;
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case ')':
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case ']':
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case '}':
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if (bracketsStack.isEmpty() || !isPaired(bracketsStack.pop(), bracket)) {
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return false;
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}
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break;
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default: /* other character is invalid */
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return false;
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}
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}
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return bracketsStack.isEmpty();
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}
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public static void main(String[] args) {
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assert isBalanced("[()]{}{[()()]()}");
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assert !isBalanced("[(])");
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}
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}
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