Problem p03298 (C++)

Buggy submission (status: Runtime Error):
#pragma GCC target("avx")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
// by piano
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 30;
int n, op[N];
char s[N];
map<string, int> tot;
int main() {
  scanf("%d", &n);
  scanf("%s", s + 1);
  tot.clear();
  for (int i = 0; i < (1 << n); i++) {
    string now = "";
    for (int j = 0; j < n; j++)
      if (!((i >> j) & 1))
        now += s[j + 1];
    now += "*";
    for (int j = n - 1; j >= 0; j--)
      if ((i >> j) & 1)
        now += s[j + 1];
    //		cout << now << endl;
    tot[now]++;
  }
  //	cout << endl;
  LL ans = 0;
  for (int i = 0; i < (1 << n); i++) {
    string now = "";
    for (int j = 0; j < n; j++)
      if ((i >> j) & 1)
        now += s[n * 2 - j];
    now += "*";
    for (int j = n - 1; j >= 0; j--)
      if (!((i >> j) & 1))
        now += s[n * 2 - j];
    //		cout << now << tot[now] << endl;
    ans += tot[now];
  }
  printf("%lld", ans);
  return 0;
}

Fixed submission:
// by piano
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 30;
int n, op[N];
char s[N];
map<string, int> tot;
int main() {
  scanf("%d", &n);
  scanf("%s", s + 1);
  tot.clear();
  for (int i = 0; i < (1 << n); i++) {
    string now = "";
    for (int j = 0; j < n; j++)
      if (!((i >> j) & 1))
        now += s[j + 1];
    now += "*";
    for (int j = n - 1; j >= 0; j--)
      if ((i >> j) & 1)
        now += s[j + 1];
    //		cout << now << endl;
    tot[now]++;
  }
  //	cout << endl;
  LL ans = 0;
  for (int i = 0; i < (1 << n); i++) {
    string now = "";
    for (int j = 0; j < n; j++)
      if ((i >> j) & 1)
        now += s[n * 2 - j];
    now += "*";
    for (int j = n - 1; j >= 0; j--)
      if (!((i >> j) & 1))
        now += s[n * 2 - j];
    //		cout << now << tot[now] << endl;
    ans += tot[now];
  }
  printf("%lld", ans);
  return 0;
}