Problem p03167 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

#define ff first
#define ss second
#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define mii map<int, int>
#define pqb priority_queue<int>
#define pqs priority_queue<int, vi, greater<int>>
#define setbits(x) __builtin_popcountll(x)
#define zrobits(x) __builtin_ctzll(x)
#define mod 1000000007
#define inf 1e18
#define ps(x, y) fixed << setprecision(y) << x
#define mk(arr, n, type) type *arr = new type[n];
#define w(x)                                                                   \
  int x;                                                                       \
  cin >> x;                                                                    \
  while (x--)
// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    pbds;

void sb() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
}

int main() {
  sb();
  int h, w;
  cin >> h >> w;
  vector<string> v;
  for (int i = 0; i < h; i++) {
    string s;
    cin >> s;
    v.push_back(s);
  }
  vector<vector<int>> dp(h, vector<int>(w, 0));
  dp[0][0] = (v[0][0] == '.');
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (v[i][j] == '.') {
        if (i > 0)
          dp[i][j] = (dp[i - 1][j] % mod + dp[i][j] % mod) % mod;
        if (j > 0)
          dp[i][j] = (dp[i][j - 1] % mod + dp[i][j] % mod) % mod;
      }
      // cout<<dp[i][j]<<" ";
    }
    // cout<<endl;
  }
  cout << dp[h - 1][w - 1];
}

Fixed submission:
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

#define ff first
#define ss second
#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define mii map<int, int>
#define pqb priority_queue<int>
#define pqs priority_queue<int, vi, greater<int>>
#define setbits(x) __builtin_popcountll(x)
#define zrobits(x) __builtin_ctzll(x)
#define mod 1000000007
#define inf 1e18
#define ps(x, y) fixed << setprecision(y) << x
#define mk(arr, n, type) type *arr = new type[n];
#define w(x)                                                                   \
  int x;                                                                       \
  cin >> x;                                                                    \
  while (x--)
// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    pbds;

void sb() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
}

int main() {
  // sb();
  int h, w;
  cin >> h >> w;
  vector<string> v;
  for (int i = 0; i < h; i++) {
    string s;
    cin >> s;
    v.push_back(s);
  }
  vector<vector<int>> dp(h, vector<int>(w, 0));
  dp[0][0] = (v[0][0] == '.');
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (v[i][j] == '.') {
        if (i > 0)
          dp[i][j] = (dp[i - 1][j] % mod + dp[i][j] % mod) % mod;
        if (j > 0)
          dp[i][j] = (dp[i][j - 1] % mod + dp[i][j] % mod) % mod;
      }
      // cout<<dp[i][j]<<" ";
    }
    // cout<<endl;
  }
  cout << dp[h - 1][w - 1];
}