Problem p00213 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <array>
#include <bitset>
#include <iostream>
#include <vector>

using namespace std;

typedef bitset<20> State;

struct Rect {
  int r, c, h, w;

  Rect() : r(0), c(0), h(0), w(0) {}
  Rect(int r, int c, int h, int w) : r(r), c(c), h(h), w(w) {}

  bool intersect(const Rect &other) const {
    return (r < other.r + other.h) && (other.r < r + h) &&
           (c < other.c + other.w) && (other.c < c + w);
  }
};

array<array<int, 16>, 16> field;
vector<Rect> ans;
vector<int> area_of;
int N, W, H;

void dfs(int r, int c, State &state, vector<Rect> &cur) {
  // cout << r << ' ' << c << endl;
  if (r == H) {
    if (ans.size() != 0)
      throw "Multiple answer";
    ans = cur;
  } else if (c == W) {
    dfs(r + 1, 0, state, cur);
  } else {
    bool conquered = false;
    for (int i = 0; i < N; ++i) {
      if (!state[i])
        continue;
      if (cur[i].intersect(Rect(r, c, 1, 1))) {
        conquered = true;
        break;
      }
    }
    if (conquered) {
      dfs(r, c + 1, state, cur);
      return;
    }
    for (int b = 0; b < N; ++b) {
      if (state[b])
        continue;
      const int area = area_of[b];
      for (int w = 1; w <= area; ++w) {
        if (area % w != 0)
          continue;
        const int h = area / w;
        const Rect cand(r, c, h, w);
        bool has_b = false;
        // Check: it is in field
        if (r + h > H || c + w > W)
          goto next;
        // Check: it contains tag b and it is only tag
        for (int dr = 0; dr < h; ++dr) {
          for (int dc = 0; dc < w; ++dc) {
            if (field[r + dr][c + dc] != 0 && field[r + dr][c + dc] != b + 1)
              goto next;
            if (field[r + dr][c + dc] == b + 1)
              has_b = true;
          }
        }
        if (!has_b)
          goto next;
        // Check: it doesn't intersect with other rects
        for (int i = 0; i < N; ++i) {
          if (!state[i])
            continue;
          if (cand.intersect(cur[i]))
            goto next;
        }
        cur[b] = cand;
        state[b] = true;
        dfs(r, c + 1, state, cur);
        state[b] = false;
      next:;
      }
    }
  }
}

bool solve() {
  cin >> W >> H >> N;
  if (!W && !H && !N)
    return false;
  area_of.clear();
  area_of.resize(N, 0);
  int area_sum = 0;
  bool na = false;
  for (int i = 0; i < N; ++i) {
    int b, k;
    cin >> b >> k;
    area_of[b - 1] = k;
    area_sum += k;
    if (b - 1 >= N)
      na = true;
  }
  for (int r = 0; r < H; ++r) {
    for (int c = 0; c < W; ++c) {
      cin >> field[r][c];
    }
  }
  if (na) {
    cout << "NA" << endl;
    return true;
  }
  try {
    if (area_sum != W * H) {
      throw "Inconsistent input";
    }
    State state;
    vector<Rect> cur(N);
    ans.clear();
    dfs(0, 0, state, cur);
    if (ans.size() == 0) {
      throw "No solution";
    }
    for (int i = 0; i < N; ++i) {
      for (int dr = 0; dr < ans[i].h; ++dr) {
        for (int dc = 0; dc < ans[i].w; ++dc) {
          field[ans[i].r + dr][ans[i].c + dc] = i + 1;
        }
      }
    }
    for (int r = 0; r < H; ++r) {
      for (int c = 0; c < W; ++c) {
        if (c != 0)
          cout << " ";
        cout << field[r][c];
      }
      cout << endl;
    }
  } catch (const char *msg) {
    // cout << msg << endl;
    cout << "NA" << endl;
  }
  return true;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);

  while (solve())
    ;
  return 0;
}

Error: WA

Fixed submission:

#include <algorithm>
#include <array>
#include <bitset>
#include <iostream>
#include <vector>

using namespace std;

typedef bitset<20> State;

struct Rect {
  int r, c, h, w;

  Rect() {}
  Rect(int r, int c, int h, int w) : r(r), c(c), h(h), w(w) {}

  bool intersect(const Rect &other) const {
    return (r < other.r + other.h) && (other.r < r + h) &&
           (c < other.c + other.w) && (other.c < c + w);
  }
};

array<array<int, 16>, 16> field;
vector<Rect> ans;
vector<int> area_of;
int N, W, H;

void dfs(int r, int c, State &state, vector<Rect> &cur) {
  // cout << r << ' ' << c << endl;
  if (r == H) {
    if (ans.size() != 0)
      throw "Multiple answer";
    ans = cur;
  } else if (c == W) {
    dfs(r + 1, 0, state, cur);
  } else if (any_of(cur.begin(), cur.end(), [r, c](const Rect &re) {
               return re.intersect(Rect(r, c, 1, 1));
             })) {
    dfs(r, c + 1, state, cur);
  } else {
    for (int b = 0; b < N; ++b) {
      if (state[b])
        continue;
      const int area = area_of[b];
      for (int w = 1; w <= area; ++w) {
        if (area % w != 0)
          continue;
        const int h = area / w;
        const Rect cand(r, c, h, w);
        bool has_b = false;
        // Check: it is in field
        if (r + h > H || c + w > W)
          goto next;
        // Check: it contains tag b and it is only tag
        for (int dr = 0; dr < h; ++dr) {
          for (int dc = 0; dc < w; ++dc) {
            if (field[r + dr][c + dc] != 0 && field[r + dr][c + dc] != b + 1)
              goto next;
            if (field[r + dr][c + dc] == b + 1)
              has_b = true;
          }
        }
        if (!has_b)
          goto next;
        // Check: it doesn't intersect with other rects
        for (int i = 0; i < N; ++i) {
          if (!state[i])
            continue;
          if (cand.intersect(cur[i]))
            goto next;
        }
        cur[b] = cand;
        state[b] = true;
        dfs(r, c + 1, state, cur);
        state[b] = false;
      next:;
      }
    }
  }
}

bool solve() {
  cin >> W >> H >> N;
  if (!W && !H && !N)
    return false;
  area_of.clear();
  area_of.resize(N, 0);
  int area_sum = 0;
  for (int i = 0; i < N; ++i) {
    int b, k;
    cin >> b >> k;
    area_of[b - 1] = k;
    area_sum += k;
  }
  for (int r = 0; r < H; ++r) {
    for (int c = 0; c < W; ++c) {
      cin >> field[r][c];
    }
  }
  try {
    if (area_sum != W * H) {
      throw "Inconsistent input";
    }
    State state;
    vector<Rect> cur(N);
    ans.clear();
    dfs(0, 0, state, cur);
    if (ans.size() == 0) {
      throw "No solution";
    }
    for (int i = 0; i < N; ++i) {
      for (int dr = 0; dr < ans[i].h; ++dr) {
        for (int dc = 0; dc < ans[i].w; ++dc) {
          field[ans[i].r + dr][ans[i].c + dc] = i + 1;
        }
      }
    }
    for (int r = 0; r < H; ++r) {
      for (int c = 0; c < W; ++c) {
        if (c != 0)
          cout << " ";
        cout << field[r][c];
      }
      cout << endl;
    }
  } catch (const char *msg) {
    // cout << msg << endl;
    cout << "NA" << endl;
  }
  return true;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);

  while (solve())
    ;
  return 0;
}