/ SeriousOJ /

Record Detail

Accepted


  
# Status Time Cost Memory Cost
#1 Accepted 1ms 532.0 KiB
#2 Accepted 1ms 508.0 KiB
#3 Accepted 2ms 580.0 KiB
#4 Accepted 21ms 8.051 MiB
#5 Accepted 29ms 6.875 MiB
#6 Accepted 36ms 8.387 MiB
#7 Accepted 371ms 96.605 MiB
#8 Accepted 259ms 68.422 MiB
#9 Accepted 85ms 96.488 MiB
#10 Accepted 269ms 96.605 MiB
#11 Accepted 2ms 532.0 KiB
#12 Accepted 279ms 96.609 MiB
#13 Accepted 115ms 77.953 MiB
#14 Accepted 16ms 3.457 MiB
#15 Accepted 360ms 96.605 MiB

Code

#include<bits/stdc++.h>
#define endl        '\n'
#define F           first
#define S           second
#define pb          push_back
#define yes         cout<<"YES\n"
#define no          cout<<"NO\n"
#define all(x)      x.begin(),x.end()
#define allr(x)     x.rbegin(),x.rend()
#define error1(x)   cerr<<#x<<" = "<<(x)<<endl
#define error2(a,b) cerr<<"("<<#a<<", "<<#b<<") = ("<<(a)<<", "<<(b)<<")\n";
#define coutall(v)  for(auto &it: v) cout << it << " "; cout << endl;
using namespace std;
using ll = long long;
using ld = long double;

const int mod = 1e9 + 7, N = 5e3 + 3;
int dp[N][N];

void solve() {
    int n, k, cnt0 = 0;
    cin >> n >> k;
    vector<bool> v(n);
    for (int i = 0; i < n; i++) {
        bool x; cin >> x;
        v[i] = x;
        cnt0 += x;
    }
    if(cnt0 < k) {
        cout << 0 << endl;
        return;
    }

    for (int i = 0; i < n; i++) {
        for(int j = max(0, k - 1); j <= n; j++) dp[i][j] = -1;
    }
    
    auto rec = [&](int i, int cnt, auto&& self) -> int {
        if(i == n or cnt < k) return 0;
        auto &ans = dp[i][cnt];
        if(ans != -1) return ans;
        ans = self(i + 1, cnt, self); // not take
        if(v[i]) ans += (cnt - 1 >= k) + self(i + 1, cnt - 1, self);
        else ans += (cnt >= k) + self(i + 1, cnt, self);
        return ans %= mod;
    };

    cout << (rec(0, cnt0, rec) + mod) % mod << endl;
    return;
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int tc = 1;
    cin >> tc;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case " << t << ": ";
        solve();
    }
    return 0;
}

Information

Submit By
Type
Submission
Problem
P1093 Number of Ways (Easy version)
Contest
Brain Booster #5
Language
C++20 (G++ 13.2.0)
Submit At
2024-09-05 17:20:18
Judged At
2024-11-11 02:58:22
Judged By
Score
100
Total Time
371ms
Peak Memory
96.609 MiB