Problem p03203 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string.h>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;

long long int INF = 1e18;
long long int mod = 1000000007;
double Pi = 3.1415926535897932384626;

vector<ll> G[500005];
vector<P> tree[500010];
priority_queue<ll> pql;
priority_queue<P> pqp;
// big priority queue
priority_queue<ll, vector<ll>, greater<ll>> pqls;
priority_queue<P, vector<P>, greater<P>> pqps;
// small priority queue
// top pop

int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
int dy[8] = {0, 1, 0, -1, 1, -1, -1, 1};
char dir[] = "RULD";
// ↓,→,↑,←

#define p(x) cout << x << endl;
#define el cout << endl;
#define pe(x) cout << x << " ";
#define ps(x) cout << fixed << setprecision(25) << x << endl;
#define pu(x) cout << x;
#define re(i, n)                                                               \
  for (i = 0; i < n; i++)                                                      \
    ;
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define deba(x) cout << #x << " = " << x << endl

ll rui(ll number1, ll number2) {
  if (number2 == 0) {
    return 1;
  } else {
    ll number3 = rui(number1, number2 / 2);
    number3 *= number3;
    number3 %= mod;
    if (number2 % 2 == 1) {
      number3 *= number1;
      number3 %= mod;
    }
    return number3;
  }
}
ll gcd(ll number1, ll number2) {
  if (number1 > number2) {
    swap(number1, number2);
  }
  if (number1 == 0 || number1 == number2) {
    return number2;
  } else {
    return gcd(number2 % number1, number1);
  }
}

ll i, j, k, ii, jj;
ll n, m, w;
ll a, b, c, d, e, g, h, r;
ll l, ans, num;
ll x[500005], y[500005], z[500005];
bool dame, flag;
char s[500005], t[500005];
bool used[505][505];
ll dp[300][300];
ll kyo;

int main() {
  cin >> h >> w >> n;
  for (i = 0; i < n; i++) {
    cin >> a >> b;
    x[i] = 300000 * a + b;
  }
  for (i = n; i < h + n; i++) {
    x[i] = 300000 * (i - n) + w + 1;
  }
  for (i = n + h; i < n + h + w; i++) {
    x[i] = 300000 * (h + 1) + (i - n - h);
  }
  n = n + h + w;
  sort(x, x + n);
  a = 1;
  b = 1;
  while (1) {
    // 下に行けるか判定
    // pe(a);p(b);
    c = lb(x, x + n, (a + 1) * 300000 + 1 + b) -
        lb(x, x + n, (a + 1) * 300000 + 1);
    if (c >= 1) {
      break;
    } else {
      a++;
    }
    // 右に動いてみる
    c = lb(x, x + n, a * 300000 + b + 2) - lb(x, x + n, a * 300000 + b + 1);
    if (c == 0)
      b++;
  }
  p(a);

  return 0;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string.h>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;

long long int INF = 1e18;
long long int mod = 1000000007;
double Pi = 3.1415926535897932384626;

vector<ll> G[500005];
vector<P> tree[500010];
priority_queue<ll> pql;
priority_queue<P> pqp;
// big priority queue
priority_queue<ll, vector<ll>, greater<ll>> pqls;
priority_queue<P, vector<P>, greater<P>> pqps;
// small priority queue
// top pop

int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
int dy[8] = {0, 1, 0, -1, 1, -1, -1, 1};
char dir[] = "RULD";
// ↓,→,↑,←

#define p(x) cout << x << endl;
#define el cout << endl;
#define pe(x) cout << x << " ";
#define ps(x) cout << fixed << setprecision(25) << x << endl;
#define pu(x) cout << x;
#define re(i, n)                                                               \
  for (i = 0; i < n; i++)                                                      \
    ;
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define deba(x) cout << #x << " = " << x << endl

ll rui(ll number1, ll number2) {
  if (number2 == 0) {
    return 1;
  } else {
    ll number3 = rui(number1, number2 / 2);
    number3 *= number3;
    number3 %= mod;
    if (number2 % 2 == 1) {
      number3 *= number1;
      number3 %= mod;
    }
    return number3;
  }
}
ll gcd(ll number1, ll number2) {
  if (number1 > number2) {
    swap(number1, number2);
  }
  if (number1 == 0 || number1 == number2) {
    return number2;
  } else {
    return gcd(number2 % number1, number1);
  }
}

ll i, j, k, ii, jj;
ll n, m, w;
ll a, b, c, d, e, g, h, r;
ll l, ans, num;
ll x[800005], y[500005], z[500005];
bool dame, flag;
char s[500005], t[500005];
bool used[505][505];
ll dp[300][300];
ll kyo;

int main() {
  cin >> h >> w >> n;
  for (i = 0; i < n; i++) {
    cin >> a >> b;
    x[i] = 300000 * a + b;
  }
  for (i = n; i < h + n; i++) {
    x[i] = 300000 * (i - n) + w + 1;
  }
  for (i = n + h; i < n + h + w; i++) {
    x[i] = 300000 * (h + 1) + (i - n - h);
  }
  n = n + h + w;
  sort(x, x + n);
  a = 1;
  b = 1;
  while (1) {
    // 下に行けるか判定
    // pe(a);p(b);
    c = lb(x, x + n, (a + 1) * 300000 + 1 + b) -
        lb(x, x + n, (a + 1) * 300000 + 1);
    if (c >= 1) {
      break;
    } else {
      a++;
    }
    // 右に動いてみる
    c = lb(x, x + n, a * 300000 + b + 2) - lb(x, x + n, a * 300000 + b + 1);
    if (c == 0)
      b++;
  }
  p(a);

  return 0;
}