Problem p00438 (C++)

Buggy submission (status: Runtime Error):

// include
//------------------------------------------
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int DX[] = {0, 1, 0, -1};
const int DY[] = {-1, 0, 1, 0};

// clear memory
#define CLR(a) memset((a), 0, sizeof(a))

// debug
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;

int main(int argc, char const *argv[]) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  string a;
  LL b;
  cin >> a >> b;
  LL length = a.length();
  LL d = (b % length);
  d = d > 0 ? d - 1 : length - 1;
  dump(d);
  cout << a[d] << endl;
  return 0;
}

Fixed submission:

// include
//------------------------------------------
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c)                                                             \
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int DX[] = {0, 1, 0, -1};
const int DY[] = {-1, 0, 1, 0};

// clear memory
#define CLR(a) memset((a), 0, sizeof(a))

// debug
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;

int main(int argc, char const *argv[]) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int width, height, n;
  while (true) {

    cin >> width >> height;
    if (width == 0 && height == 0) {
      break;
    }
    cin >> n;
    vector<PII> bad(n);
    VVI table(height, VI(width));
    REP(i, n) {
      int x, y;
      cin >> x >> y;
      x--;
      y = height - y;
      table[y][x] = -1;
    }
    table[height - 1][0] = 1;
    int value;
    for (int y = height - 1; y >= 0; --y) {
      REP(x, width) {
        if (table[y][x] == -1)
          continue;
        if (x > 0) {
          value = table[y][x - 1];
          table[y][x] += value > -1 ? value : 0;
        }
        if (y < height - 1) {
          value = table[y + 1][x];
          table[y][x] += value > -1 ? value : 0;
        }
      }
    }
    cout << table[0][width - 1] << endl;
  }

  return 0;
}