Problem p00742 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
typedef ll li;
typedef pair<int, int> PI;
#define EPS (1e-6)
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define REP(i, n) rep(i, n)
#define F first
#define S second
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define min3(a, b, c) min((a), min((b), (c)))
#define min4(a, b, c, d) min((a), min3((b), (c), (d)))
#define SZ(a) (int)((a).size())
#define ALL(a) a.begin(), a.end()
#define FLL(a, b) memset((a), b, sizeof(a))
#define CLR(a) memset((a), 0, sizeof(a))
#define FOR(it, a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)
template <typename T, typename U>
ostream &operator<<(ostream &out, const pair<T, U> &val) {
  return out << "(" << val.F << ", " << val.S << ")";
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &val) {
  out << "{";
  rep(i, SZ(val)) out << (i ? ", " : "") << val[i];
  return out << "}";
}
typedef double FP;
typedef complex<FP> pt;
typedef pt P;
typedef pair<pt, pt> line;
FP dot(P a, P b) { return real(conj(a) * b); }
FP crs(P a, P b) { return imag(conj(a) * b); }
P ortho(P a) { return conj(P(imag(a), real(a))); }
P ortho(line a) { return ortho(a.S - a.F); }
P crspt(P a, P b, P c, P d) {
  b -= a, d -= c;
  return a + b * crs(d, c - a) / crs(d, b);
}
P crspt(line a, line b) { return crspt(a.F, a.S, b.F, b.S); }
bool onl(P a1, P a2, P b) {
  return abs(b - a1) + abs(b - a2) < abs(a1 - a2) + EPS;
}
bool onl(line a, P b) { return onl(a.F, a.S, b); }
bool iscrs(line a, line b) {
  P c = crspt(a, b);
  return onl(a, c) && onl(b, c);
}
void pkuassert(bool t) { t = 1 / t; };
int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
int dy[] = {1, 0, -1, 0, -1, 1, 1, -1};
enum { TOP, BTM, LFT, RGT, FRT, BCK };
int dxdy2ce[] = {RGT, FRT, LFT, BCK};
template <class T> T shift(T a, int b, int c, int d, int e) {
  __typeof(a[0]) t = a[b];
  a[b] = a[c];
  a[c] = a[d];
  a[d] = a[e];
  a[e] = t;
  return a;
}
template <class T> T rgt(T a) { return shift(a, TOP, LFT, BTM, RGT); }
template <class T> T lft(T a) { return shift(a, TOP, RGT, BTM, LFT); }
template <class T> T frt(T a) { return shift(a, TOP, BCK, BTM, FRT); }
template <class T> T bck(T a) { return shift(a, TOP, FRT, BTM, BCK); }
line mkl(P a, P v) { return line(a, a + v); }
FP lpdist(line a, P b) { return abs(b - crspt(a, mkl(b, ortho(a)))); }

FP spdist(line a, P b) {
  P c(crspt(a, mkl(b, ortho(a))));
  return onl(a, c) ? abs(b - c) : min(abs(a.F - b), abs(a.S - b));
}

FP ssdist(line a, line b) {
  return min4(spdist(a, b.F), spdist(a, b.S), spdist(b, a.F), spdist(b, a.S));
}

int n;
string in[10];
int ans;
int used[10];
int vis[300];
void dfs(int ne, int le, int c) {
  if (le == 10) {
    bool ok = 1;
    rep(i, n) ok &= SZ(in[i]) < 2 || vis[(int)in[i][SZ(in[i]) - 1]] != 1;
    ans += ok;
    return;
  }

  if (ne == n) {
    int su = c;
    rep(i, n - 1) if (le < SZ(in[i])) su += vis[(int)in[i][le]] - 1;
    int wa = 0;
    if (le < SZ(in[n - 1]))
      wa = vis[(int)in[n - 1][le]] - 1;
    if (su % 10 != wa)
      return;
    c = su / 10;
    ne = 0;
    ++le;
  }
  if (SZ(in[ne]) <= le) {
    dfs(ne + 1, le, c);
    return;
  }

  if (vis[(int)in[ne][le]]) {
    dfs(ne + 1, le, c);
    return;
  }

  rep(i, 10) {
    if (used[i])
      continue;
    used[i] = 1;
    vis[(int)in[ne][le]] = i + 1;
    dfs(ne + 1, le, c);
    vis[(int)in[ne][le]] = 0;
    used[i] = 0;
  }
}

void solve() {
  rep(i, n) cin >> in[i];
  rep(i, n) reverse(ALL(in[i]));
  ans = 0;
  dfs(0, 0, 0);
  cout << ans << endl;
}

int main(int argc, char *argv[]) {
  while (cin >> n && n)
    solve();
  return 0;
}

Fixed submission:
#include <algorithm>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
typedef ll li;
typedef pair<int, int> PI;
#define EPS (1e-6)
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define REP(i, n) rep(i, n)
#define F first
#define S second
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define min3(a, b, c) min((a), min((b), (c)))
#define min4(a, b, c, d) min((a), min3((b), (c), (d)))
#define SZ(a) (int)((a).size())
#define ALL(a) a.begin(), a.end()
#define FLL(a, b) memset((a), b, sizeof(a))
#define CLR(a) memset((a), 0, sizeof(a))
#define FOR(it, a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)
template <typename T, typename U>
ostream &operator<<(ostream &out, const pair<T, U> &val) {
  return out << "(" << val.F << ", " << val.S << ")";
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &val) {
  out << "{";
  rep(i, SZ(val)) out << (i ? ", " : "") << val[i];
  return out << "}";
}
typedef double FP;
typedef complex<FP> pt;
typedef pt P;
typedef pair<pt, pt> line;
FP dot(P a, P b) { return real(conj(a) * b); }
FP crs(P a, P b) { return imag(conj(a) * b); }
P ortho(P a) { return conj(P(imag(a), real(a))); }
P ortho(line a) { return ortho(a.S - a.F); }
P crspt(P a, P b, P c, P d) {
  b -= a, d -= c;
  return a + b * crs(d, c - a) / crs(d, b);
}
P crspt(line a, line b) { return crspt(a.F, a.S, b.F, b.S); }
bool onl(P a1, P a2, P b) {
  return abs(b - a1) + abs(b - a2) < abs(a1 - a2) + EPS;
}
bool onl(line a, P b) { return onl(a.F, a.S, b); }
bool iscrs(line a, line b) {
  P c = crspt(a, b);
  return onl(a, c) && onl(b, c);
}
void pkuassert(bool t) { t = 1 / t; };
int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
int dy[] = {1, 0, -1, 0, -1, 1, 1, -1};
enum { TOP, BTM, LFT, RGT, FRT, BCK };
int dxdy2ce[] = {RGT, FRT, LFT, BCK};
template <class T> T shift(T a, int b, int c, int d, int e) {
  __typeof(a[0]) t = a[b];
  a[b] = a[c];
  a[c] = a[d];
  a[d] = a[e];
  a[e] = t;
  return a;
}
template <class T> T rgt(T a) { return shift(a, TOP, LFT, BTM, RGT); }
template <class T> T lft(T a) { return shift(a, TOP, RGT, BTM, LFT); }
template <class T> T frt(T a) { return shift(a, TOP, BCK, BTM, FRT); }
template <class T> T bck(T a) { return shift(a, TOP, FRT, BTM, BCK); }
line mkl(P a, P v) { return line(a, a + v); }
FP lpdist(line a, P b) { return abs(b - crspt(a, mkl(b, ortho(a)))); }

FP spdist(line a, P b) {
  P c(crspt(a, mkl(b, ortho(a))));
  return onl(a, c) ? abs(b - c) : min(abs(a.F - b), abs(a.S - b));
}

FP ssdist(line a, line b) {
  return min4(spdist(a, b.F), spdist(a, b.S), spdist(b, a.F), spdist(b, a.S));
}

int n;
string in[20];
int ans;
int used[10];
int vis[300];
void dfs(int ne, int le, int c) {
  if (le == 10) {
    bool ok = 1;
    rep(i, n) ok &= SZ(in[i]) < 2 || vis[(int)in[i][SZ(in[i]) - 1]] != 1;
    ans += ok;
    return;
  }

  if (ne == n) {
    int su = c;
    rep(i, n - 1) if (le < SZ(in[i])) su += vis[(int)in[i][le]] - 1;
    int wa = 0;
    if (le < SZ(in[n - 1]))
      wa = vis[(int)in[n - 1][le]] - 1;
    if (su % 10 != wa)
      return;
    c = su / 10;
    ne = 0;
    ++le;
  }
  if (SZ(in[ne]) <= le) {
    dfs(ne + 1, le, c);
    return;
  }

  if (vis[(int)in[ne][le]]) {
    dfs(ne + 1, le, c);
    return;
  }

  rep(i, 10) {
    if (used[i])
      continue;
    used[i] = 1;
    vis[(int)in[ne][le]] = i + 1;
    dfs(ne + 1, le, c);
    vis[(int)in[ne][le]] = 0;
    used[i] = 0;
  }
}

void solve() {
  rep(i, n) cin >> in[i];
  rep(i, n) reverse(ALL(in[i]));
  ans = 0;
  dfs(0, 0, 0);
  cout << ans << endl;
}

int main(int argc, char *argv[]) {
  while (cin >> n && n)
    solve();
  return 0;
}