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32.java
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32.java
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public class Solution {
public int longestValidParentheses(String s) {
int ret = 0;
Stack<Integer> st = new Stack();
int [] dp = new int[s.length()];
for(int i = 0; i< s.length(); ++i) {
dp[i] = -1;
if(s.charAt(i) != '(' && s.charAt(i) != ')') {
st.clear();
continue;
}
//System.out.println(s.charAt(i));
if(s.charAt(i) == '('){
st.push(i);
}
else {
if(!st.isEmpty()) {
int curIndex = st.pop();
dp[i] = curIndex;
}
}
}
for(int i = s.length() - 1; i >= 0; i--) {
if(dp[i] == -1) continue;
int l = i - dp[i] + 1;
int lb = dp[i] - 1;
while(lb>= 0 && dp[lb] != -1) {
l += lb - dp[lb] + 1;
lb = dp[lb] - 1;
i = lb;
}
if(l > ret) ret = l;
}
return ret;
}
}