Array Description ( CSES )

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <climits>
#include <queue>
using namespace std;
const int N = 1e5, mod = 1e9 + 7;
int dp[N][101], a[N+1], n, m, ans = 0;
void read()
{
   cin >> n >> m;
   for (int i = 1; i <= n; ++ i)
   {
       cin >> a[i];
   }
}
void solve()
{
    if (a[1] == 0)
    {
        for (int i = 1; i <= m; ++ i)
        {
            dp[1][i] = 1;
        }
    }
    else
    {
        dp[1][a[1]] = 1;
    }
    for (int i = 2; i <= n; ++ i)
    {
        if (a[i] == 0)
        {
            for (int j = 1; j <= m; ++ j)
            {
                for (int k : {j - 1, j, j + 1})
                    {
                        if (k >= 1 && k <= m)
                        {
                            dp[i][j] = (dp[i][j] + dp[i-1][k]) % mod;
                        }
                    }
            }
        }
        else
        {
            for (int k : {a[i] - 1, a[i], a[i] + 1})
                {
                    if (k >= 1 && k <= m)
                    {
                        dp[i][a[i]] = (dp[i][a[i]] + dp[i-1][k]) % mod;;
                    }
                }
        }
    }
    for (int i = 1; i <= m; ++ i)
    {
        ans = (ans + dp[n][i]) % mod;
    }
    cout << ans;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    read();
    solve();
}