Submission #419773

#	Time	Username	Problem	Language	Result	Execution time	Memory
419773		Kerim	Group Photo (JOI21_ho_t3)	C++17	100 / 100	2431 ms	788692 KiB

Main

#include "bits/stdc++.h"
#define MAXN 100009
#define INF 1000000007
#define mp(x,y) make_pair(x,y)
#define all(v) v.begin(),v.end()
#define pb(x) push_back(x)
#define wr cout<<"----------------"<<endl;
#define ppb() pop_back()
#define tr(ii,c) for(__typeof((c).begin()) ii=(c).begin();ii!=(c).end();ii++)
#define ff first
#define ss second
#define my_little_dodge 46
#define debug(x)  cerr<< #x <<" = "<< x<<endl;
using namespace std;
 
typedef long long ll;
typedef pair<int,int> PII;
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
const int N=5002;
int n,arr[N],inv[N][N],dp[N][N],odp[N][N],suf[N][N];
int F[N][N],AB[N][N],BA[N][N],par[N][N],G[N][N];
int g(int x,int y){
	if(x>=y)return 0;
	if(~odp[x][y])return odp[x][y];
	return odp[x][y]=g(x,y-1)+par[y][y]-par[x-1][y];
}
int cost(int a,int b){
	return g(a+1,b-1)+F[a][b-1]+(BA[b][b-1]-BA[b][a]);
}
int main(){
	//freopen("file.in", "r", stdin);
	memset(odp,-1,sizeof odp);
	scanf("%d",&n);
	for(int i=1;i<=n;i++)scanf("%d",arr+i);
	for(int i=2;i<=n;i++)
		for(int j=1;j<i;j++)
			inv[arr[i]][arr[j]]++;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			par[i][j]=par[i-1][j]+inv[j][i];
	for(int z=1;z<=n;z++)
		for(int x=1;x<=n;x++)
			G[x][z]=G[x-1][z]+inv[x][z];
	for(int y=1;y<=n;y++)
		for(int z=y+1;z<=n;z++)
			F[y][z]=F[y][z-1]+G[y][z];
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++){
			BA[i][j]=BA[i][j-1]+inv[i][j];
			AB[i][j]=AB[i][j-1]+inv[j][i];
		}
	for(int a=n;a>=0;a--){
		for(int b=a+1;b<=n;b++){
			if(b==n)
				dp[a][b]=cost(a,b);
			else
				dp[a][b]=suf[b][b+1]+cost(a,b);
		}
		suf[a][n+1]=INF;
		for(int i=n;i>a;i--)
			suf[a][i]=min(suf[a][i+1],dp[a][i]+AB[i][a]);
	}
	
	int ans=INF;
	for(int i=1;i<=n;i++)
		umin(ans,dp[0][i]);
	printf("%d\n",ans);
	return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:34:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |  scanf("%d",&n);
      |  ~~~~~^~~~~~~~~
Main.cpp:35:28: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |  for(int i=1;i<=n;i++)scanf("%d",arr+i);
      |                       ~~~~~^~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36