Submission #1674740

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Source Code Expand

#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iterator>
#include <bitset>
#include <unordered_set>
#include <unordered_map>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <utility>
#include <memory>
#include <functional>
#include <deque>
#include <cctype>
#include <ctime>
#include <numeric>
#include <list>
#include <iomanip>

#if __cplusplus >= 201103L
#include <array>
#include <tuple>
#include <initializer_list>
#include <forward_list>

#define cauto const auto&
#else

#endif

using namespace std;


typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<long long> vll;
typedef vector<vector<long long> > vvll;

#define VV(T) vector<vector< T > >

template <class T>
void initvv(vector<vector<T> > &v, int a, int b, const T &t = T()){
    v.assign(a, vector<T>(b, t));
}

template <class F, class T>
void convert(const F &f, T &t){
    stringstream ss;
    ss << f;
    ss >> t;
}

#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _rep(i,n) _rep2((i),0,(n))
#define _rep2(i,a,b) for(int i=(a);i<(b);++i)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define fi first
#define se second
#define mkp make_pair
#define DEBUG
#ifdef DEBUG
#define dump(x)  cout << #x << " = " << (x) << endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#else
#define dump(x) 
#define debug(x) 
#endif

#define MOD 1000000007LL
#define EPS 1e-8
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
#define maxs(x,y) x=max(x,y)
#define mins(x,y) x=min(x,y)

int dp[4010][2010];

template<class T>
struct RollingHash {
	static const int NN = 2; // the number of hash table
	T base[NN] = {1009, 1007};
	T PMOD[NN] = {1000000007, 1000000009};
	vector<T> hash[NN];
	vector<T> mypow[NN];
	int sz;
	void init(string s) {
		sz = s.size();
		for(int i = 0; i < NN; i++) {
			hash[i].assign(sz + 1, 0);
			mypow[i].assign(sz + 1, 0);
			mypow[i][0] = 1;
		}
		for(int i = 0; i < NN; i++) {
			for(int j = 0; j < sz; j++) {
				hash[i][j + 1] = (hash[i][j] * base[i] + s[j]) % PMOD[i];
				mypow[i][j + 1] = mypow[i][j] * base[i] % PMOD[i];
			}
		}
	}
	RollingHash() {
	}
	// hash[t] value of s[l..r]
	T get(int l, int r, int t) {
		T ret = (hash[t][r + 1] - hash[t][l] * mypow[t][r - l + 1] % PMOD[t] + PMOD[t]) % PMOD[t];
		return ret;
	}
	// compare s[a..b] and s[c..d] O(1)
	bool comp(int a, int b, int c, int d) {
		if(a < 0 || sz <= b || c < 0 || sz <= d) return false;
		for(int i = 0; i < NN; i++) {
			if(get(a, b, i) != get(c, d, i)) return false;
		}
		return true;
	}
	// longest common extension s[l..LCE(l,r)] == s[r..LCE(l,r)] && s[l..LCE(l,r)+1] != s[r..LCE(l,r)+1]
	int LCE(int l,int r){
		// cout<<l<<" "<<r<<endl;
		if(l>r) swap(l,r);
		// tie(l,r)=minmax(l,r);
		// cout<<l<<" "<<r<<endl;
		// if(l==5&&r==3){
			// cout<<"hoge"<<endl;
			// cout<<"ll "<<ll<<endl;
		// }
		if(l==r) return sz-r+1;
		int ll = 0;
		int rr = sz;
		while(rr-ll>1){
			int mid = (ll+rr)>>1;
			if(comp(l,l+mid-1,r,r+mid-1)) ll=mid;
			else rr=mid;
		}
		return ll;
	}
};


RollingHash<ll> rh;

int compare(int x, int y, int n, string &s){
	if(x==-1) return 1;
	if(rh.comp(x, x+n-1, y, y+n-1)){
		return 0;
	}
	// assert(x<n&&y<n);
	int len = rh.LCE(x, y);
	// if(x==5&&y==3){
		// cout<<"len "<<len<<endl;
		// cout<<"aa "<<s[x]<<" "<<s[y]<<endl;
	// }
	if(s[x+len]<s[y+len]) return -1;
	return 1;
}

int compare2(int x, int y, int n, string &s){
	rep(i,n){
		if(s[x+i]!=s[y+i]){
			if(s[x+i]<s[y+i]) return 1;
			else return 0;
		}
	}
	return 0;
}

void mainmain(){
	int K;
	cin>>K;
	string s;
	cin>>s;
	if(K==0){
		cout<<s<<endl;
		return;
	}
	K++;
	int n = s.size();
	int m = n/K;
	int a = n%K;
	// cout<<m<<" "<<a<<endl;
	assert(n<=2000);
	rh.init(s);
	if(a==0){
		int ans = 0;
		rep(i,n){
			int p = i*m;
			if(p>=n) break;
			if(compare2(ans, p, m, s)==1) ans = p;
		}
		cout<<s.substr(ans, m)<<endl;
		return;
	}
	rep(i,2*n+1) rep(j,K+1) dp[i][j]=-1;
	rep(i,1,n){
		if(i*m>=n) break;
		dp[i*m+1][1] = (i-1)*m;
		// cout<<i*m+1<<" "<<n<<endl;
	}
	// cout<<dp[n][1]<<endl;
	rep(i,n){
		// cout<<i<<endl;
		rep(j,K){
			// cout<<"j "<<j<<endl;
			if(dp[i][j]==-1) continue;
			if(compare(dp[i+m][j], dp[i][j], m+1, s)==1){
				dp[i+m][j] = dp[i][j];
			}
			int p;
			if(compare(dp[i][j], i, m+1, s)==-1) p=i;
			else p=dp[i][j];
			// if(i==5&&j==1) cout<<"p "<<p<<" "<<dp[i+m+1][j+1]<<endl;
			if(compare(dp[i+m+1][j+1], p, m+1, s)==1){
				dp[i+m+1][j+1] = p;
			}
			// if(i==5&&j==1) cout<<"p "<<p<<" "<<dp[i+m+1][j+1]<<endl;
		}
	}
	// cout<<dp[n][a]<<endl;
	// cout<<dp[3][1]<<endl;
	// cout<<dp[5][1]<<endl;
	// cout<<dp[8][2]<<endl;
	cout<<s.substr(dp[n][a],m+1)<<endl;
}


signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(20);
    mainmain();
}

Submission Info

Judge Result