544C - Writing Code - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define MOEZ ios_base::sync_with_stdio(false);cin.tie(NULL),cout.tie(NULL);
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define F first
#define S second
#define pb push_back
#define all(v) v.begin() , v.end()
#define eb emplace_back
#define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());}
#define mem(d , x) memset(d , x , sizeof(d));
#define sz(x) (int)x.size()
const int N = 1e3+5;
//const int M = 1e9+7;
//const ll inf = 1e18;
//const ld eps = 1e-6;
#define int long long
int n , m , b , M , a[501];
int dp[2][501][501];
signed main(){
    MOEZ
    cin >> n >> m >> b >> M;
    for(int i = 0; i < n;i++){
        cin >> a[i];
    }
    dp[0][0][0] = 1;
    bool f = true;
    for(int i = 0; i < n;i++){
        for(int j = 0; j <= m;j++){
            for(int k = 0; k <= b;k++){
                dp[f][j][k] = dp[(f^1)][j][k];
                if(j && k-a[i] >= 0){
                    dp[f][j][k] += dp[f][j-1][k-a[i]];
                }
                dp[f][j][k] %= M;
            }
        }
        f ^= 1;
    }
    int ans = 0;
    for(int i = 0; i <= b;i++){
        ans += dp[(f^1)][m][i];
        ans %= M;
    }
    cout << ans;
}