Problem p03256 (C++)

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

#define li long long int
#define rep(i, to) for (li i = 0; i < ((li)(to)); i++)
#define repp(i, start, to) for (li i = (li)(start); i < ((li)(to)); i++)
#define pb push_back
#define sz(v) ((li)(v).size())
#define bgn(v) ((v).begin())
#define eend(v) ((v).end())
#define allof(v) (v).begin(), (v).end()
#define dodp(v, n) memset(v, (li)n, sizeof(v))
#define bit(n) (1ll << (li)(n))
#define mp(a, b) make_pair(a, b)
#define rin rep(i, n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1

#define idp if (DBGP)
#define F first
#define S second
#define p2(a, b) idp cout << a << "\t" << b << endl
#define p3(a, b, c) idp cout << a << "\t" << b << "\t" << c << endl
#define p4(a, b, c, d)                                                         \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << endl
#define p5(a, b, c, d, e)                                                      \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << endl
#define p6(a, b, c, d, e, f)                                                   \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << endl
#define p7(a, b, c, d, e, f, g)                                                \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << endl
#define p8(a, b, c, d, e, f, g, h)                                             \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << endl
#define p9(a, b, c, d, e, f, g, h, i)                                          \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << "\t" << i << endl
#define p10(a, b, c, d, e, f, g, h, i, j)                                      \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << "\t" << i << "\t" << j << endl
#define foreach(it, v)                                                         \
  for (__typeof((v).begin()) it = (v).begin(); it != (v).end(); ++it)
#define p2p(x) idp p2((x).F, (x).S)
#define dump(x, n)                                                             \
  idp {                                                                        \
    rep(i, n) { cout << x[i] << " "; }                                         \
    puts("");                                                                  \
  }
#define dump2(x, n)                                                            \
  idp {                                                                        \
    rep(i, n) { cout << "[" << x[i].F << " , " << x[i].S << "] "; }            \
    puts("");                                                                  \
  }
#define dumpi(x)                                                               \
  idp {                                                                        \
    foreach (it, x) {                                                          \
      cout << (*it) << " ";                                                    \
    }                                                                          \
    puts("");                                                                  \
  }
#define dumpi2(x)                                                              \
  idp {                                                                        \
    foreach (it, x) {                                                          \
      cout << "[" << (it)->F << " , " << (it)->S << "] ";                      \
    }                                                                          \
    puts("");                                                                  \
  }

#define read2d(a, w, h) rep(i, h) rep(j, w) cin >> a[i][j]
#define dump2d(a, w, h)                                                        \
  rep(i, h) {                                                                  \
    rep(j, w) cout << a[i][j] << " ";                                          \
    puts("");                                                                  \
  }

typedef pair<li, li> PI;

li n, m;
bool isa[200200];

set<li> edge[200200][2];

inline bool ok(li x) { return (!edge[x][0].empty() && !edge[x][1].empty()); }

inline void prune(li x) {
  vector<li> remove_list;
  rep(i, 2) {
    foreach (it, edge[x][i]) {
      li next = *it;
      edge[next][(isa[x] ? 0 : 1)].erase(x);
      remove_list.pb(next);
    }
    edge[x][i].clear();
  }
  rep(i, sz(remove_list)) {
    if (!ok(remove_list[i]) && remove_list[i] != x) {
      prune(remove_list[i]);
    }
  }
}

int main() {
  cin >> n >> m;
  string s;
  cin >> s;
  rep(i, sz(s)) { isa[i] = (s[i] == 'A'); }
  rep(i, m) {
    li x, y;
    cin >> x >> y;
    x--;
    y--;
    if (isa[y]) {
      edge[x][0].insert(y);
    } else {
      edge[x][1].insert(y);
    }
    if (isa[x]) {
      edge[y][0].insert(x);
    } else {
      edge[y][1].insert(x);
    }
  }

  rin {
    if (!ok(i)) {
      prune(i);
    }
  }
  bool res = false;
  rin {
    if (ok(i)) {
      res = true;
      break;
    }
  }
  cout << (res ? "Yes" : "No") << endl;
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

#define li long long int
#define rep(i, to) for (li i = 0; i < ((li)(to)); i++)
#define repp(i, start, to) for (li i = (li)(start); i < ((li)(to)); i++)
#define pb push_back
#define sz(v) ((li)(v).size())
#define bgn(v) ((v).begin())
#define eend(v) ((v).end())
#define allof(v) (v).begin(), (v).end()
#define dodp(v, n) memset(v, (li)n, sizeof(v))
#define bit(n) (1ll << (li)(n))
#define mp(a, b) make_pair(a, b)
#define rin rep(i, n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1

#define idp if (DBGP)
#define F first
#define S second
#define p2(a, b) idp cout << a << "\t" << b << endl
#define p3(a, b, c) idp cout << a << "\t" << b << "\t" << c << endl
#define p4(a, b, c, d)                                                         \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << endl
#define p5(a, b, c, d, e)                                                      \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << endl
#define p6(a, b, c, d, e, f)                                                   \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << endl
#define p7(a, b, c, d, e, f, g)                                                \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << endl
#define p8(a, b, c, d, e, f, g, h)                                             \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << endl
#define p9(a, b, c, d, e, f, g, h, i)                                          \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << "\t" << i << endl
#define p10(a, b, c, d, e, f, g, h, i, j)                                      \
  idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t"    \
           << f << "\t" << g << "\t" << h << "\t" << i << "\t" << j << endl
#define foreach(it, v)                                                         \
  for (__typeof((v).begin()) it = (v).begin(); it != (v).end(); ++it)
#define p2p(x) idp p2((x).F, (x).S)
#define dump(x, n)                                                             \
  idp {                                                                        \
    rep(i, n) { cout << x[i] << " "; }                                         \
    puts("");                                                                  \
  }
#define dump2(x, n)                                                            \
  idp {                                                                        \
    rep(i, n) { cout << "[" << x[i].F << " , " << x[i].S << "] "; }            \
    puts("");                                                                  \
  }
#define dumpi(x)                                                               \
  idp {                                                                        \
    foreach (it, x) {                                                          \
      cout << (*it) << " ";                                                    \
    }                                                                          \
    puts("");                                                                  \
  }
#define dumpi2(x)                                                              \
  idp {                                                                        \
    foreach (it, x) {                                                          \
      cout << "[" << (it)->F << " , " << (it)->S << "] ";                      \
    }                                                                          \
    puts("");                                                                  \
  }

#define read2d(a, w, h) rep(i, h) rep(j, w) cin >> a[i][j]
#define dump2d(a, w, h)                                                        \
  rep(i, h) {                                                                  \
    rep(j, w) cout << a[i][j] << " ";                                          \
    puts("");                                                                  \
  }

typedef pair<li, li> PI;

li n, m;
bool isa[200200];

set<li> edge[200200][2];

inline bool ok(li x) { return (!edge[x][0].empty() && !edge[x][1].empty()); }

inline void prune(li x) {
  vector<li> remove_list;
  rep(i, 2) {
    foreach (it, edge[x][i]) {
      li next = *it;
      if (next == x)
        continue;
      edge[next][(isa[x] ? 0 : 1)].erase(x);
      remove_list.pb(next);
    }
    edge[x][i].clear();
  }
  rep(i, sz(remove_list)) {
    if (!ok(remove_list[i]) && remove_list[i] != x) {
      prune(remove_list[i]);
    }
  }
}

int main() {
  cin >> n >> m;
  string s;
  cin >> s;
  rep(i, sz(s)) { isa[i] = (s[i] == 'A'); }
  rep(i, m) {
    li x, y;
    cin >> x >> y;
    x--;
    y--;
    if (isa[y]) {
      edge[x][0].insert(y);
    } else {
      edge[x][1].insert(y);
    }
    if (isa[x]) {
      edge[y][0].insert(x);
    } else {
      edge[y][1].insert(x);
    }
  }

  rin {
    if (!ok(i)) {
      prune(i);
    }
  }
  bool res = false;
  rin {
    if (ok(i)) {
      res = true;
      break;
    }
  }
  cout << (res ? "Yes" : "No") << endl;
  return 0;
}