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@@ -1,5 +1,23 @@
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+import java.util.*;
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+
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class Solution {
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public int longestValidParentheses(String s) {
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-
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+ char[] chs = s.toCharArray();
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+ Stack<Integer> stack = new Stack<>();
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+ int max = 0, pre = -1;
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+ for (int i = 0; i < chs.length; i++) {
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+ if (chs[i] == '(') {
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+ stack.push(i);
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+ continue;
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+ }
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+ if (stack.empty()) {
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+ pre = i;
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+ continue;
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+ }
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+ stack.pop();
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+ if (stack.empty()) max = Math.max(max, i - pre);
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+ else max = Math.max(max, i - stack.peek());
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+ }
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+ return max;
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}
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}
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