Problem p03640 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
#define REP(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int(i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for (int(i) = (a)-1; (i) >= 0; (i)--)
#define FORR(i, a, b) for (int(i) = (a)-1; (i) >= (b); (i)--)
#define DEBUG(C) cerr << #C << " = " << C << endl;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<LL>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using PII = pair<int, int>;
using PDD = pair<double, double>;
using PLL = pair<LL, LL>;
using VPII = vector<PII>;
template <typename T> using VT = vector<T>;
#define ALL(a) begin((a)), end((a))
#define RALL(a) rbegin((a)), rend((a))
#define SORT(a) sort(ALL((a)))
#define RSORT(a) sort(RALL((a)))
#define REVERSE(a) reverse(ALL((a)))
#define MP make_pair
#define FORE(a, b) for (auto &&a : (b))
#define FIND(s, e) ((s).find(e) != (s).end())
#define EB emplace_back
template <typename T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;

const int MAX = 111;
int n, h, w;
int c[MAX][MAX];
int a[MAX];

PII next() {
  static int nowH = -1, nowW = 0, nextD = -1;
  if ((nowW == w - 1 && nextD == 1) || (nowW == 0 && nextD == -1)) {
    nextD *= -1;
    nowH++;
  } else
    nowW += nextD;
  PII res = MP(nowH, nowW);
  return res;
}

int main(void) {
  scanf("%d%d", &h, &w);
  scanf("%d", &n);
  REP(i, n) { scanf("%d", a + i); }
  int now = 0;
  REP(i, n) {
    REP(j, a[i]) {
      int nh, nw;
      tie(nh, nw) = next();
      // cerr << nh << " " << nw << endl;
      c[nh][nw] = i + 1;
    }
  }
  REP(i, h) REP(j, w) { printf("%d%c", c[i][j], (j + 1 == w ? '\n' : ' ')); }
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
#define REP(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int(i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for (int(i) = (a)-1; (i) >= 0; (i)--)
#define FORR(i, a, b) for (int(i) = (a)-1; (i) >= (b); (i)--)
#define DEBUG(C) cerr << #C << " = " << C << endl;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<LL>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using PII = pair<int, int>;
using PDD = pair<double, double>;
using PLL = pair<LL, LL>;
using VPII = vector<PII>;
template <typename T> using VT = vector<T>;
#define ALL(a) begin((a)), end((a))
#define RALL(a) rbegin((a)), rend((a))
#define SORT(a) sort(ALL((a)))
#define RSORT(a) sort(RALL((a)))
#define REVERSE(a) reverse(ALL((a)))
#define MP make_pair
#define FORE(a, b) for (auto &&a : (b))
#define FIND(s, e) ((s).find(e) != (s).end())
#define EB emplace_back
template <typename T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;

const int MAX = 111;
int n, h, w;
int c[MAX][MAX];
int a[MAX * MAX];

PII next() {
  static int nowH = -1, nowW = 0, nextD = -1;
  if ((nowW == w - 1 && nextD == 1) || (nowW == 0 && nextD == -1)) {
    nextD *= -1;
    nowH++;
  } else
    nowW += nextD;
  PII res = MP(nowH, nowW);
  return res;
}

int main(void) {
  scanf("%d%d", &h, &w);
  scanf("%d", &n);
  REP(i, n) { scanf("%d", a + i); }
  int now = 0;
  REP(i, n) {
    REP(j, a[i]) {
      int nh, nw;
      tie(nh, nw) = next();
      // cerr << nh << " " << nw << endl;
      c[nh][nw] = i + 1;
    }
  }
  REP(i, h) REP(j, w) { printf("%d%c", c[i][j], (j + 1 == w ? '\n' : ' ')); }
}