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Commitb4f77c2

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applewjg
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LongestValidParentheses
Change-Id: I4f04cf277e6b91fb7e3dbb377f824237fb96b26c
1 parent8fd268f commitb4f77c2

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‎LongestValidParentheses.java

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/*
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Author: King, wangjingui@outlook.com
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Date: Dec 20, 2014
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Problem: Longest Valid Parentheses
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Difficulty: Easy
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Source: https://oj.leetcode.com/problems/longest-valid-parentheses/
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Notes:
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Given a string containing just the characters '(' and ')', find the length of the longest valid
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(well-formed) parentheses substring.
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For "(()", the longest valid parentheses substring is "()", which has length = 2.
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Another example is ")()())", where the longest valid parentheses substring is "()()",
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which has length = 4.
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Solution: O(n).
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*/
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publicclassSolution {
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publicintlongestValidParentheses_1(Strings) {
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Stack<Integer>stk =newStack<Integer>();
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intres =0,count =0;
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for(inti =0;i <s.length(); ++i) {
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if (s.charAt(i) =='(') {
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stk.push(count);
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count =0;
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}elseif (stk.empty() ==false) {
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count += (1 +stk.pop());
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res =Math.max(res,count);
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}else {
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count =0;
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}
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}
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returnres *2;
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}
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publicintlongestValidParentheses(Strings) {
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intn =s.length();
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if (n <=1)return0;
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intres =0;
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int[]f =newint[n];
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for(inti=n-2;i>=0;i--){
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intmatch =i +f[i+1] +1;
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if(match<n&&s.charAt(i)=='('&&s.charAt(match)==')'){
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f[i]=f[i+1]+2;
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if(match+1<n)f[i]+=f[match+1];
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}
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res =Math.max(res,f[i]);
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}
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returnres;
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}
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}

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