代码

#include <bits/stdc++.h>

using namespace std;

unsigned solve(int n, char *s) {
  vector<unsigned> dp = {1};
  for (int i = 0; i < n; ++i) {
    vector<unsigned> pd(min(i + 2, n - i));
    if (s[i] != ')') {
      for (int j = i & 1; j < dp.size(); j += 2) {
        if (j + 1 < pd.size()) {
          pd[j + 1] += dp[j];
        }
      }
    }
    if (s[i] != '(') {
      for (int j = i & 1; j < dp.size(); j += 2) {
        if (j > 0) {
          pd[j - 1] += dp[j];
        }
      }
    }
    dp = pd;
  }
  return dp[0];
}

评测结果