Problem p00950 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

#define _overload(_1, _2, _3, name, ...) name
#define _rep(i, n) _range(i, 0, n)
#define _range(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload(__VA_ARGS__, _range, _rep, )(__VA_ARGS__)

#define _rrep(i, n) _rrange(i, n, 0)
#define _rrange(i, a, b) for (int i = (int)(a)-1; i >= (int)(b); --i)
#define rrep(...) _overload(__VA_ARGS__, _rrange, _rrep, )(__VA_ARGS__)

#define _all(arg) begin(arg), end(arg)
#define uniq(arg) sort(_all(arg)), (arg).erase(unique(_all(arg)), end(arg))
#define getidx(ary, key) lower_bound(_all(ary), key) - begin(ary)
#define clr(a, b) memset((a), (b), sizeof(a))
#define bit(n) (1LL << (n))

// #define DEBUG

#ifdef DEBUG
#define dump(...) fprintf(stderr, __VA_ARGS__)
#else
#define dump(...)
#endif

template <class T> bool chmax(T &a, const T &b) {
  return (a < b) ? (a = b, 1) : 0;
}
template <class T> bool chmin(T &a, const T &b) {
  return (b < a) ? (a = b, 1) : 0;
}

using namespace std;
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;

const double EPS = 1e-10;
const double PI = acos(-1.0);
const ll inf = 1LL << 62;
const ll mod = 1000000007LL;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll extgcd(ll a, ll b, ll &x, ll &y) {
  x = 1, y = 0;
  ll g = a;
  if (b != 0)
    g = extgcd(b, a % b, y, x), y -= a / b * x;
  return g;
}
ll ADD(const ll &a, const ll &b, const ll &mod) { return (a + b) % mod; }
ll SUB(const ll &a, const ll &b, const ll &mod) { return (a - b + mod) % mod; }
ll MUL(const ll &a, const ll &b, const ll &mod) { return (1LL * a * b) % mod; }
ll DIV(const ll &a, const ll &b, const ll &mod) {
  ll x, y;
  extgcd(b, mod, x, y);
  return MUL(a, (x + mod) % mod, mod);
}

random_device rd;
mt19937 mt(rd());
uniform_int_distribution<int> dice(1, 6);
uniform_real_distribution<double> score(0.0, 10.0);

string f;
int idx, len;

int number();
int factor();
int term();
int expression();

int number() {
  char c = f[idx++];
  if (c != '0' and c != '1')
    throw 1;

  if (c == '0')
    return 0;

  int ret = 1;
  while (idx < len and (f[idx] == '0' or f[idx] == '1')) {
    ret *= 2;
    char c = f[idx++];
    if (c == '1')
      ret += 1;
  }
  return ret;
}

int factor() {
  int mcnt = 0;
  while (idx < len and f[idx] == '-') {
    mcnt++;
    idx++;
  }
  if (idx >= len)
    throw 1;

  int sign = (mcnt % 2 == 0 ? +1 : -1);
  if (f[idx] != '(')
    return sign * number();
  idx++;

  int ret = sign * expression();
  if (idx >= len or f[idx] != ')')
    throw 1;
  idx++;

  return ret;
}

int term() {
  int ret = factor();
  while (idx < len and f[idx] == '*') {
    idx++;
    int rhs = factor();
    ret *= rhs;
  }
  return ret;
}

int expression() {
  int ret = term();
  while (idx < len and (f[idx] == '+' or f[idx] == '-')) {
    char op = f[idx++];
    int rhs = term();
    switch (op) {
    case '+': {
      ret += rhs;
      break;
    }
    case '-': {
      ret -= rhs;
      break;
    }
    }
  }
  return ret;
}

int main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  /*
  while(cin >> f){
      len = f.size(), idx = 0;
      int ret = expression();
      cerr << ret << ", idx = " << idx << ", len = " << len << endl;
  }
  return 0;
  //*/

  string in;
  cin >> in;
  string T = "01+-*()=";
  sort(_all(T));

  set<string> s;
  do {
    map<char, bool> used;
    map<char, char> c2t;
    int j = 0;
    f = in;
    rep(i, in.size()) {
      char c = in[i];
      if (not isupper(c) and not islower(c))
        continue;

      if (not used[c]) {
        used[c] = true;
        assert(j < T.size());
        c2t[c] = T[j++];
      }
      f[i] = c2t[c];
    }

    string equation = f;
    string l, r;
    rep(i, in.size()) {
      if (f[i] == '=') {
        l = f.substr(0, i);
        r = f.substr(i + 1);
        break;
      }
    }
    if (l == "" or r == "")
      continue;

    try {
      idx = 0;
      f = l;
      len = f.size();
      int lv = expression();
      if (idx != len)
        continue;

      idx = 0;
      f = r;
      len = f.size();
      int rv = expression();
      if (idx != len)
        continue;

      if (lv != rv)
        continue;
    } catch (int e) {
      continue;
    }
    s.insert(equation);
  } while (next_permutation(_all(T)));

  // for(auto& e : s){
  //     cerr << e << endl;
  // }
  cout << s.size() << endl;

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>

#define _overload(_1, _2, _3, name, ...) name
#define _rep(i, n) _range(i, 0, n)
#define _range(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload(__VA_ARGS__, _range, _rep, )(__VA_ARGS__)

#define _rrep(i, n) _rrange(i, n, 0)
#define _rrange(i, a, b) for (int i = (int)(a)-1; i >= (int)(b); --i)
#define rrep(...) _overload(__VA_ARGS__, _rrange, _rrep, )(__VA_ARGS__)

#define _all(arg) begin(arg), end(arg)
#define uniq(arg) sort(_all(arg)), (arg).erase(unique(_all(arg)), end(arg))
#define getidx(ary, key) lower_bound(_all(ary), key) - begin(ary)
#define clr(a, b) memset((a), (b), sizeof(a))
#define bit(n) (1LL << (n))

// #define DEBUG

#ifdef DEBUG
#define dump(...) fprintf(stderr, __VA_ARGS__)
#else
#define dump(...)
#endif

template <class T> bool chmax(T &a, const T &b) {
  return (a < b) ? (a = b, 1) : 0;
}
template <class T> bool chmin(T &a, const T &b) {
  return (b < a) ? (a = b, 1) : 0;
}

using namespace std;
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;

const double EPS = 1e-10;
const double PI = acos(-1.0);
const ll inf = 1LL << 62;
const ll mod = 1000000007LL;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll extgcd(ll a, ll b, ll &x, ll &y) {
  x = 1, y = 0;
  ll g = a;
  if (b != 0)
    g = extgcd(b, a % b, y, x), y -= a / b * x;
  return g;
}
ll ADD(const ll &a, const ll &b, const ll &mod) { return (a + b) % mod; }
ll SUB(const ll &a, const ll &b, const ll &mod) { return (a - b + mod) % mod; }
ll MUL(const ll &a, const ll &b, const ll &mod) { return (1LL * a * b) % mod; }
ll DIV(const ll &a, const ll &b, const ll &mod) {
  ll x, y;
  extgcd(b, mod, x, y);
  return MUL(a, (x + mod) % mod, mod);
}

random_device rd;
mt19937 mt(rd());
uniform_int_distribution<int> dice(1, 6);
uniform_real_distribution<double> score(0.0, 10.0);

string f;
int idx, len;

int number();
int factor();
int term();
int expression();

int number() {
  char c = f[idx++];
  if (c != '0' and c != '1')
    throw 1;

  if (c == '0')
    return 0;

  int ret = 1;
  while (idx < len and (f[idx] == '0' or f[idx] == '1')) {
    ret *= 2;
    char c = f[idx++];
    if (c == '1')
      ret += 1;
  }
  return ret;
}

int factor() {
  int mcnt = 0;
  while (idx < len and f[idx] == '-') {
    mcnt++;
    idx++;
  }
  if (idx >= len)
    throw 1;

  int sign = (mcnt % 2 == 0 ? +1 : -1);
  if (f[idx] != '(')
    return sign * number();
  idx++;

  int ret = sign * expression();
  if (idx >= len or f[idx] != ')')
    throw 1;
  idx++;

  return ret;
}

int term() {
  int ret = factor();
  while (idx < len and f[idx] == '*') {
    idx++;
    int rhs = factor();
    ret *= rhs;
  }
  return ret;
}

int expression() {
  int ret = term();
  while (idx < len and (f[idx] == '+' or f[idx] == '-')) {
    char op = f[idx++];
    int rhs = term();
    switch (op) {
    case '+': {
      ret += rhs;
      break;
    }
    case '-': {
      ret -= rhs;
      break;
    }
    }
  }
  return ret;
}

int main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  /*
  while(cin >> f){
      len = f.size(), idx = 0;
      int ret = expression();
      cerr << ret << ", idx = " << idx << ", len = " << len << endl;
  }
  return 0;
  //*/

  string in;
  cin >> in;
  string T = "01+-*()=";
  sort(_all(T));

  set<string> s;
  do {
    map<char, bool> used;
    map<char, char> c2t;
    int j = 0;
    f = in;
    rep(i, in.size()) {
      char c = in[i];
      if (not isupper(c) and not islower(c))
        continue;

      if (not used[c]) {
        used[c] = true;
        if (j >= T.size()) {
          cout << 0 << endl;
          return 0;
        }
        c2t[c] = T[j++];
      }
      f[i] = c2t[c];
    }

    string equation = f;
    string l, r;
    rep(i, in.size()) {
      if (f[i] == '=') {
        l = f.substr(0, i);
        r = f.substr(i + 1);
        break;
      }
    }
    if (l == "" or r == "")
      continue;

    try {
      idx = 0;
      f = l;
      len = f.size();
      int lv = expression();
      if (idx != len)
        continue;

      idx = 0;
      f = r;
      len = f.size();
      int rv = expression();
      if (idx != len)
        continue;

      if (lv != rv)
        continue;
    } catch (int e) {
      continue;
    }
    s.insert(equation);
  } while (next_permutation(_all(T)));

  // for(auto& e : s){
  //     cerr << e << endl;
  // }
  cout << s.size() << endl;

  return 0;
}