64 lines
1.2 KiB
Java
64 lines
1.2 KiB
Java
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import java.util.Scanner;
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/**
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* Given a string containing just the characters '(' and ')', find the length of
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* the longest valid (well-formed) parentheses substring.
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*
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*
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* @author Libin Yang (https://github.com/yanglbme)
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* @since 2018/10/5
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*/
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public class LongestValidParentheses {
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public static int getLongestValidParentheses(String s) {
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if (s == null || s.length() < 2) {
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return 0;
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}
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char[] chars = s.toCharArray();
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int n = chars.length;
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int[] res = new int[n];
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res[0] = 0;
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res[1] = chars[1] == ')' && chars[0] == '(' ? 2 : 0;
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int max = res[1];
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for (int i = 2; i < n; ++i) {
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if (chars[i] == ')') {
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if (chars[i - 1] == '(') {
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res[i] = res[i - 2] + 2;
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} else {
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int index = i - res[i - 1] - 1;
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if (index >= 0 && chars[index] == '(') {
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// ()(())
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res[i] = res[i - 1] + 2 + (index - 1 >= 0 ? res[index - 1] : 0);
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}
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}
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}
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max = Math.max(max, res[i]);
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}
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return max;
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}
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public static void main(String[] args) {
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Scanner sc = new Scanner(System.in);
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while (true) {
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String str = sc.nextLine();
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if ("quit".equals(str)) {
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break;
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}
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int len = getLongestValidParentheses(str);
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System.out.println(len);
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}
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sc.close();
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}
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}
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