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