Submission #59017137

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Source Code Expand

#include <bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
#define all(a) a.begin(),a.end()
typedef long long ll;
typedef pair<ll,ll> P;
typedef modint1000000007 mi;
constexpr ll mod=1000000007;

class char_index{
	public:
	char c;
	int index;

	bool operator< (const char_index& a) const{
		if(c<a.c)return true;
		if(c>a.c)return false;
		return index<a.index;
	}
	bool operator>(const char_index& a) const{
		if(c<a.c)return false;
		if(c>a.c)return true;
		return index>a.index;
	}
};

int main(){
	int n,k;cin>>n>>k;
	string s;cin>>s;
	set<char_index> S;
	rep(i,n-k)S.insert({s[i],i});
	string ans;

	int l=0;

	rep(i,k){
		S.insert({s[n+i-k],n+i-k});
		auto min_c=S.begin();
		ans.push_back((*min_c).c);
		int r=(*min_c).index;
		for(int j=l;j<=r;j++){
			S.erase({s[j],j});
		}
		l=r+1;
	}
	cout<<ans<<endl;
}

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