Problem p02686 (C++) — buggy submission, verdict: Runtime Error

/*input
3
(((
)
)
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

#pragma GCC optimize("unroll-loops,no-stack-protector")
// order_of_key #of elements less than x
//  find_by_order kth element
typedef long long int ll;
#define ld long double
#define pii pair<ll, ll>
typedef tree<pii, null_type, less<pii>, rb_tree_tag,
             tree_order_statistics_node_update>
    indexed_set;
#define f first
#define s second
#define pb push_back
#define REP(i, n) for (ll i = 0; i < n; i++)
#define REP1(i, n) for (int i = 1; i <= n; i++)
#define FILL(n, x) memset(n, x, sizeof(n))
#define ALL(_a) _a.begin(), _a.end()
#define sz(x) (int)x.size()
const int maxn = 1e6 + 5;
const int maxlg = __lg(maxn) + 2;
const ll INF64 = 4e18;
const int INF = 0x3f3f3f3f;
const ll MOD = 1e9 + 7;
const ld PI = acos(-1);
const ld eps = 1e-9;
#define lowb(x) x & (-x)
#define MNTO(x, y) x = min(x, (__typeof__(x))y)
#define MXTO(x, y) x = max(x, (__typeof__(x))y)
#define SORT_UNIQUE(c)                                                         \\
  (sort(c.begin(), c.end()),                                                   \\
   c.resize(distance(c.begin(), unique(c.begin(), c.end()))))
#define GET_POS(c, x) (lower_bound(c.begin(), c.end(), x) - c.begin())
ll mult(ll a, ll b) { return (a * b) % MOD; }
ll mypow(ll a, ll b) {
  if (b <= 0)
    return 1;
  ll res = 1LL;
  while (b) {
    if (b & 1)
      res = mult(res, a);
    a = mult(a, a);
    b >>= 1;
  }
  return res;
}
string s[maxn];
int cnt[maxn];
bool cmp(pair<int, string> &a, pair<int, string> &b) {
  int cr = sz(a.s) - a.f, br = sz(b.s) - b.f;
  return (a.f - cr) < (b.f - br);
}
bool cmp2(string &a, string &b) { return sz(a) > sz(b); }
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  int n;
  cin >> n;
  REP(i, n) {
    cnt[i] = 0;
    string tmp;
    cin >> tmp;
    vector<char> st;
    REP(j, sz(tmp)) {
      if (!sz(st) or !(st.back() == '(' and tmp[j] == ')')) {
        st.pb(tmp[j]);
      } else {
        st.pop_back();
      }
    }
    s[i] = "";
    REP(j, sz(st)) {
      if (st[j] == ')')
        cnt[i]++;
      s[i] += st[j];
    }
  }
  string ans = "";
  REP(i, n) {
    if (sz(s[i]) and s[i][0] == '(') {
      ans += s[i];
    }
  }
  vector<pair<int, string>> v;
  REP(i, n) {
    if (sz(s[i]) and s[i][0] == ')' and s[i].back() == '(') {
      v.pb({cnt[i], s[i]});
    }
  }
  sort(ALL(v), cmp);
  REP(i, sz(v)) { ans += v[i].s; }
  REP(i, n) {
    if (sz(s[i]) and s[i][0] == ')' and s[i].back() != '(') {
      ans += s[i];
    }
  }
  stack<char> st;
  REP(j, sz(ans)) {
    if (!sz(st) or !(st.top() == '(' and ans[j] == ')')) {
      st.push(ans[j]);
    } else {
      st.pop();
    }
  }
  if (sz(st))
    cout << "No";
  else
    cout << "Yes";
}


Error: WA

Fixed submission:

/*input
3
(((
)
)
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

#pragma GCC optimize("unroll-loops,no-stack-protector")
// order_of_key #of elements less than x
//  find_by_order kth element
typedef long long int ll;
#define ld long double
#define pii pair<ll, ll>
typedef tree<pii, null_type, less<pii>, rb_tree_tag,
             tree_order_statistics_node_update>
    indexed_set;
#define f first
#define s second
#define pb push_back
#define REP(i, n) for (ll i = 0; i < n; i++)
#define REP1(i, n) for (int i = 1; i <= n; i++)
#define FILL(n, x) memset(n, x, sizeof(n))
#define ALL(_a) _a.begin(), _a.end()
#define sz(x) (int)x.size()
const int maxn = 2e5 + 5;
const int maxlg = __lg(maxn) + 2;
const ll INF64 = 4e18;
const int INF = 0x3f3f3f3f;
const ll MOD = 1e9 + 7;
const ld PI = acos(-1);
const ld eps = 1e-9;
#define lowb(x) x & (-x)
#define MNTO(x, y) x = min(x, (__typeof__(x))y)
#define MXTO(x, y) x = max(x, (__typeof__(x))y)
#define SORT_UNIQUE(c)                                                         \\
  (sort(c.begin(), c.end()),                                                   \\
   c.resize(distance(c.begin(), unique(c.begin(), c.end()))))
#define GET_POS(c, x) (lower_bound(c.begin(), c.end(), x) - c.begin())
ll mult(ll a, ll b) { return (a * b) % MOD; }
ll mypow(ll a, ll b) {
  if (b <= 0)
    return 1;
  ll res = 1LL;
  while (b) {
    if (b & 1)
      res = mult(res, a);
    a = mult(a, a);
    b >>= 1;
  }
  return res;
}
string s[maxn];
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  int n;
  cin >> n;
  REP(i, n) {
    string tmp;
    cin >> tmp;
    vector<char> st;
    REP(j, sz(tmp)) {
      if (!sz(st) or !(st.back() == '(' and tmp[j] == ')')) {
        st.pb(tmp[j]);
      } else {
        st.pop_back();
      }
    }
    s[i] = "";
    REP(j, sz(st)) { s[i] += st[j]; }
  }
  string ans = "";
  REP(i, n) {
    if (sz(s[i]) and s[i][0] == '(') {
      ans += s[i];
    }
  }
  REP(i, n) {
    if (sz(s[i]) and s[i][0] != '(') {
      ans += s[i];
    }
  }
  stack<char> st;
  REP(j, sz(ans)) {
    if (!sz(st) or !(st.top() == '(' and ans[j] == ')')) {
      st.push(ans[j]);
    } else {
      st.pop();
    }
  }
  if (sz(st))
    cout << "No";
  else
    cout << "Yes";
}