Problem p03685 (C++)

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

#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (int x = (l); x <= (u); x++)
#define RREP(x, l, u) for (int x = (l); x >= (u); x--)
#define mst(x, a) memset(x, a, sizeof(x))
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define PIII pair<PII, int>
#define MP make_pair
#define se second
#define fi first
#define dbg(x) cout << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define cl(x) x.clear()

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;

const int maxn = 100010;
const int mod = 1e9 + 7;
const int MAX = 1000000010;
const double eps = 1e-6;
const double PI = acos(-1);

template <typename T> inline void read(T &x) {
  x = 0;
  T f = 1;
  char ch;
  do {
    ch = getchar();
    if (ch == '-')
      f = -1;
  } while (ch < '0' || ch > '9');
  do
    x = x * 10 + ch - '0', ch = getchar();
  while (ch <= '9' && ch >= '0');
  x *= f;
}

template <typename A, typename B> inline void read(A &x, B &y) {
  read(x);
  read(y);
}
template <typename A, typename B, typename C>
inline void read(A &x, B &y, C &z) {
  read(x);
  read(y);
  read(z);
}
template <typename A, typename B, typename C, typename D>
inline void read(A &x, B &y, C &z, D &w) {
  read(x);
  read(y);
  read(z);
  read(w);
}
template <typename A, typename B> inline A fexp(A x, B p) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mod)
    if (p & 1)
      ans = 1LL * ans * x % mod;
  return ans;
}
template <typename A, typename B> inline A fexp(A x, B p, A mo) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mo)
    if (p & 1)
      ans = 1LL * ans * x % mo;
  return ans;
}

int R, C, n, cnt;

PIII has[maxn];

int s[maxn], top;

int calc(PII x) {
  if (x.fi == 0)
    return x.se;
  if (x.se == C)
    return C + x.fi;
  if (x.fi == R)
    return C + R + C - x.se;
  return C + R + C + R - x.fi;
}

bool cmp(PIII x, PIII y) { return calc(x.fi) < calc(y.fi); }

bool Is(int x, int y) { return x == 0 || y == 0 || x == R || y == C; }

void Work() {
  sort(has + 1, has + cnt + 1, cmp);
  //	REP(i,1,cnt)cout<<has[i].se<<' '<<has[i].fi.fi<<' '<<has[i].fi.se<<'
  //'<<calc(has[i].fi)<<endl;cout<<endl;
  REP(i, 1, cnt) {
    if (top && s[top] == has[i].se)
      top--;
    else
      s[++top] = has[i].se;
  }
  if (top)
    puts("NO");
  else
    puts("YES");
}

void Init() {
  read(R, C, n);
  REP(i, 1, n) {
    int x1, y1, x2, y2;
    read(x1, y1, x2, y2);
    if (Is(x1, y1) && Is(x2, y2)) {
      has[++cnt] = MP(MP(x1, y1), i);
      has[++cnt] = MP(MP(x2, y2), i);
    }
  }
}

int main() {
  Init();
  Work();
  return 0;
}


Fixed submission:
#include "bits/stdc++.h"

#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (int x = (l); x <= (u); x++)
#define RREP(x, l, u) for (int x = (l); x >= (u); x--)
#define mst(x, a) memset(x, a, sizeof(x))
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define PIII pair<PII, int>
#define MP make_pair
#define se second
#define fi first
#define dbg(x) cout << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define cl(x) x.clear()

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;

const int maxn = 200010;
const int mod = 1e9 + 7;
const int MAX = 1000000010;
const double eps = 1e-6;
const double PI = acos(-1);

template <typename T> inline void read(T &x) {
  x = 0;
  T f = 1;
  char ch;
  do {
    ch = getchar();
    if (ch == '-')
      f = -1;
  } while (ch < '0' || ch > '9');
  do
    x = x * 10 + ch - '0', ch = getchar();
  while (ch <= '9' && ch >= '0');
  x *= f;
}

template <typename A, typename B> inline void read(A &x, B &y) {
  read(x);
  read(y);
}
template <typename A, typename B, typename C>
inline void read(A &x, B &y, C &z) {
  read(x);
  read(y);
  read(z);
}
template <typename A, typename B, typename C, typename D>
inline void read(A &x, B &y, C &z, D &w) {
  read(x);
  read(y);
  read(z);
  read(w);
}
template <typename A, typename B> inline A fexp(A x, B p) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mod)
    if (p & 1)
      ans = 1LL * ans * x % mod;
  return ans;
}
template <typename A, typename B> inline A fexp(A x, B p, A mo) {
  A ans = 1;
  for (; p; p >>= 1, x = 1LL * x * x % mo)
    if (p & 1)
      ans = 1LL * ans * x % mo;
  return ans;
}

int R, C, n, cnt;

PIII has[maxn];

int s[maxn], top;

int calc(PII x) {
  if (x.fi == 0)
    return x.se;
  if (x.se == C)
    return C + x.fi;
  if (x.fi == R)
    return C + R + C - x.se;
  return C + R + C + R - x.fi;
}

bool cmp(PIII x, PIII y) { return calc(x.fi) < calc(y.fi); }

bool Is(int x, int y) { return x == 0 || y == 0 || x == R || y == C; }

void Work() {
  sort(has + 1, has + cnt + 1, cmp);
  //	REP(i,1,cnt)cout<<has[i].se<<' '<<has[i].fi.fi<<' '<<has[i].fi.se<<'
  //'<<calc(has[i].fi)<<endl;cout<<endl;
  REP(i, 1, cnt) {
    if (top && s[top] == has[i].se)
      top--;
    else
      s[++top] = has[i].se;
  }
  if (top)
    puts("NO");
  else
    puts("YES");
}

void Init() {
  read(R, C, n);
  REP(i, 1, n) {
    int x1, y1, x2, y2;
    read(x1, y1, x2, y2);
    if (Is(x1, y1) && Is(x2, y2)) {
      has[++cnt] = MP(MP(x1, y1), i);
      has[++cnt] = MP(MP(x2, y2), i);
    }
  }
}

int main() {
  Init();
  Work();
  return 0;
}