Submission #418929

#	Time	Username	Problem	Language	Result	Execution time	Memory
418929		lyc	Skyscraper (JOI16_skyscraper)	C++14	100 / 100	221 ms	130404 KiB

skyscraper

#include <bits/stdc++.h>
using namespace std;

#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for(int i=(a);i>=(b);--i)
const int mod = 1e9+7;

const int mxN = 105;
const int mxL = 1005;
const int mxA = 1005;

int N, L, A[mxN];
int res[mxN][mxN][mxL][3];

// processing ith element, j connected component, k cost, l ends open
int dp(int i, int j, int k, int l) {
    if (k > L || l < 0) return 0;
    if (i > N) return j == 1 && l == 0;

    int& ans = res[i][j][k][l];
    if (~ans) return ans;
    ans = 0;

    int opened = 2*j - 2 + l;
    int kk = k + opened * (A[i]-A[i-1]);

    // new cc
    ans += (long long) (j+1 - 2 + l) * dp(i+1, j+1, kk, l) % mod;
    ans %= mod;
    ans += l * dp(i+1, j+1, kk, l-1) % mod;
    ans %= mod;

    if (j > 0) {
        // append
        ans += (long long) opened * dp(i+1, j, kk, l) % mod;
        ans %= mod;
        ans += l * dp(i+1, j, kk, l-1) % mod;
        ans %= mod;
    }

    if (j > 1) {
        // join
        ans += (long long) (j-1) * dp(i+1, j-1, kk, l) % mod;
        ans %= mod;
    }

    //TRACE(i _ j _ k _ l _ ans);
    return ans;
}

int main() {
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

    cin >> N >> L;
    FOR(i,1,N){
        cin >> A[i];
    }

    // corner case -- cannot close both ends simultaneously
    if (N == 1) {
        cout << 1 << '\n';
        return 0;
    }

    sort(A+1,A+1+N);
    memset(res,-1,sizeof res);
    cout << dp(1,0,0,2) << '\n';
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 80 / 80