32

include/solution/32.h

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+// This file is generated by mkfile.py
+// Date: 2026-06-26
+
+#ifndef INC_32_H
+#define INC_32_H
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+    int longestValidParentheses(char *s);
+#ifdef __cplusplus
+}
+#endif
+#endif // INC_32_H

src/32.c

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+// This file is generated by mkfile.py
+// Date: 2026-06-26
+
+#include <solution/32.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#define max(x, y) ((x) > (y) ? (x) : (y))
+
+int longestValidParentheses(char *s)
+{
+    int result = 0;
+    int m = strlen(s);
+
+    if (m < 2)
+        return result;
+
+    int *dp = malloc(sizeof(int) * m);
+    memset(dp, 0, sizeof(int) * m);
+
+    //     i: current index, we skipped 0 because one char can not
+    //        be paired
+    // dp[i]: use i as the end of string, see how much parentheses
+    //        can be matched before i
+    for (int i = 1; i < m; i++)
+    {
+        // if current char is "(" it can not be matched, a valid
+        // match must be ended with ")". we just check s[i] == ')'
+        if (s[i] == ')')
+        {
+            // so there are 2 match situations:
+            // 1. s[i - 1] == '('. it can match current ')'. we also
+            //    need to check before it if we had a valid pair.
+            if (s[i - 1] == '(')
+            {
+                if (i > 1)
+                    dp[i] = dp[i - 2] + 2;
+                else
+                    dp[i] = 2;
+                continue;
+            }
+            // 2. s[i - 1] == ')'. it means there maybe has valid pair
+            //    before. we need to know how much pairs before i. we
+            //    can read it from dp[i], then we can get char before
+            //    valid pair. like situation 1, if char == '(' it can
+            //    be matched. but we need to noticed, if there is no
+            //    valid pair before, this ')' must be ignored.
+            int k = i - dp[i - 1] - 1;
+            if (k < 0)
+                continue;
+
+            if (s[k] == '(')
+            {
+                // if k > 1, see if we can add a valid pair before k
+                if (k > 1)
+                    dp[i] = dp[i - 1] + dp[k - 1] + 2;
+                else
+                    dp[i] = dp[i - 1] + 2;
+            }
+        }
+    }
+
+    for (int i = 0; i < m; i++)
+        result = max(dp[i], result);
+
+    free(dp);
+    return result;
+}

tests/test_32.cpp

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+// This file is generated by mkfile.py
+// Date: 2026-06-26
+
+#include <gtest/gtest.h>
+#include <solution/32.h>
+
+#include <string>
+#include <vector>
+
+class LongestValidParenthesesTest : public ::testing::Test
+{
+  protected:
+    void AssertLongestValidParentheses(const std::string &input, int expected)
+    {
+        std::vector<char> buffer(input.begin(), input.end());
+        buffer.push_back('\0');
+
+        EXPECT_EQ(longestValidParentheses(buffer.data()), expected);
+    }
+};
+
+TEST_F(LongestValidParenthesesTest, Example1)
+{
+    AssertLongestValidParentheses("(()", 2);
+}
+
+TEST_F(LongestValidParenthesesTest, Example2)
+{
+    AssertLongestValidParentheses(")()())", 4);
+}
+
+TEST_F(LongestValidParenthesesTest, Example3)
+{
+    AssertLongestValidParentheses("", 0);
+}
+
+TEST_F(LongestValidParenthesesTest, ReturnsZeroWhenThereIsNoValidPair)
+{
+    AssertLongestValidParentheses("(", 0);
+    AssertLongestValidParentheses(")", 0);
+    AssertLongestValidParentheses("((((", 0);
+    AssertLongestValidParentheses("))))", 0);
+    AssertLongestValidParentheses(")(", 0);
+}
+
+TEST_F(LongestValidParenthesesTest, EntireStringIsValid)
+{
+    AssertLongestValidParentheses("()", 2);
+    AssertLongestValidParentheses("()()", 4);
+    AssertLongestValidParentheses("(())", 4);
+    AssertLongestValidParentheses("(()())", 6);
+}
+
+TEST_F(LongestValidParenthesesTest, FindsValidSubstringAfterInvalidPrefix)
+{
+    AssertLongestValidParentheses(")()", 2);
+    AssertLongestValidParentheses("())(())", 4);
+    AssertLongestValidParentheses("())()()", 4);
+}
+
+TEST_F(LongestValidParenthesesTest, FindsLongestContiguousSubstring)
+{
+    AssertLongestValidParentheses("()(()", 2);
+    AssertLongestValidParentheses("(()(((()", 2);
+    AssertLongestValidParentheses("(()())())", 8);
+    AssertLongestValidParentheses("()(())", 6);
+}
+
+TEST_F(LongestValidParenthesesTest, HandlesMultipleSeparatedValidBlocks)
+{
+    AssertLongestValidParentheses("()(()())", 8);
+    AssertLongestValidParentheses("())(()())", 6);
+    AssertLongestValidParentheses("(()())())(()(()))", 8);
+}