Submission #225412

#	Time	Username	Problem	Language	Result	Execution time	Memory
225412		brcode	Skyscraper (JOI16_skyscraper)	C++14	100 / 100	274 ms	403960 KiB

skyscraper

#include <iostream>
#include <bits/stdc++.h>

using namespace std;
const long long MAXN = 110;
const long long MOD = 1e9+7;
long long dp[MAXN][MAXN][1010][5];
long long arr[MAXN];
long long n,L;
long long rec(long long i,long long j,long long k,long long l){
    //dp[i][j][k][l] = first i numbers, j connected components, k = total sum and l = number of endpolong longs on which numbers have been placed
    if(i>0 && (j<1||l>2||k>L)){
        return 0;
    }
    if(i==n){
        
        return (j==1 && l==2);
    }
    if(dp[i][j][k][l]!=-1){
        return dp[i][j][k][l];
    }
    long long toadd = (arr[i+1]-arr[i])*(2*j-l) + k;//all positions adjacent to existing connected components must be incremented by the difference between adjacent elements in our array
    dp[i][j][k][l] = 0;
    dp[i][j][k][l] = (dp[i][j][k][l] + ((2*j-l)%MOD*rec(i+1,j,toadd,l)%MOD)%MOD)%MOD;//add on to an already existing connected component
    dp[i][j][k][l] = (dp[i][j][k][l] + ((j+1-l)%MOD*rec(i+1,j+1,toadd,l)%MOD)%MOD)%MOD;//add a new connected component
    dp[i][j][k][l] = (dp[i][j][k][l] + ((2-l)%MOD*rec(i+1,j+1,toadd,l+1)%MOD)%MOD)%MOD;//add a new connected component to an endpolong long
    dp[i][j][k][l] = (dp[i][j][k][l] + ((2-l)%MOD*rec(i+1,j,toadd,l+1)%MOD)%MOD)%MOD;//extend an already existing connected component to an endpolong long
    dp[i][j][k][l] = (dp[i][j][k][l] + ((j-1)%MOD*rec(i+1,j-1,toadd,l)%MOD)%MOD)%MOD;//merge 2 connected components
    return dp[i][j][k][l];
}
int main(){
    cin>>n>>L;
    for(long long i=1;i<=n;i++){
        cin>>arr[i];
    }
    sort(arr+1,arr+n+1);
    for(long long i=0;i<=n;i++){
        for(long long j=0;j<=n;j++){
            for(long long k=0;k<=L;k++){
                for(long long l=0;l<=3;l++){
                    dp[i][j][k][l] = -1;
                }
            }
        }
    }
    if(n==1){
        cout<<1<<endl;
        return 0;
    }
    cout<<rec(0,0,0,0)<<endl;
}

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