diff --git a/Dynamic Programming/LongestValidParentheses.java b/Dynamic Programming/LongestValidParentheses.java index 14c98020..1a42b258 100644 --- a/Dynamic Programming/LongestValidParentheses.java +++ b/Dynamic Programming/LongestValidParentheses.java @@ -1,63 +1,59 @@ - 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; + 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]; + 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]); - } + 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; + return max; - } + } - public static void main(String[] args) { - Scanner sc = new Scanner(System.in); + 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); + while (true) { + String str = sc.nextLine(); + if ("quit".equals(str)) { + break; + } + int len = getLongestValidParentheses(str); + System.out.println(len); - } - - sc.close(); - - } + } + sc.close(); + } }