Submission #3439181

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Source Code Expand

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

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

#define fi first
#define se second
#define repl(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define rep(i,n) repl(i,0,n)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define mmax(x,y) (x>y?x:y)
#define mmin(x,y) (x<y?x:y)
#define maxch(x,y) x=mmax(x,y)
#define minch(x,y) x=mmin(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt __builtin_popcountll

#define INF 1e16
#define mod 1000000007

struct UnionFind{
  vector<int> v;
  UnionFind(int n) : v(n, -1) {}
  void init(){ for(int i = 0;i < (int)v.size();i++)v[i]=-1; }
  int find(int x) { return v[x] < 0 ? x : v[x] = find(v[x]); }
  bool unite(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return false;
    if (-v[x] < -v[y]) swap(x, y);
    v[x] += v[y]; v[y] = x;
    return true;
  }
  bool root(int x) { return v[x] < 0; }
  bool same(int x, int y) { return find(x) == find(y); }
  int size(int x) { return -v[find(x)]; }
};

ll N;
ll A[200010];
vector<ll> pre[200010];
char c[200010];

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

  cin>>N;
  rep(i,N)cin>>A[i];
  UnionFind uf(N);
  rep(i,N){
    if(A[i]>1&&i-1>=0&&i+1<N){
      uf.unite(i-1,i+1);
    }
    if(A[i]>=5&&i-2>=0&&i+2<N){
      uf.unite(i-2,i+2);
    }
    ll l=i-((A[i]+1)/2);
    ll r=i+((A[i]+1)/2);
    if(l+1>0&&r-1<N){
      uf.unite(l+1,r-1);
    }
    if(l+2>0&&r-2<N){
      uf.unite(l+2,r-2);
    }
    if(l<0||r>=N)continue;
    pre[r].push_back(l);
  }
  rep(i,N){
    if(c[uf.find(i)]!=0){
      c[i]=c[uf.find(i)]; continue;
    }
    vector<bool> used(26,false);
    for(int p : pre[i]){
      used[c[p]-'a']=true;
    }
    rep(j,26){
      if(!used[j]){
        c[i]=(char)j+'a';
        break;
      }
    }
    assert(c[i]>0);
  }
  rep(i,N)cout<<c[i];
  cout<<endl;

  return 0;
}

Submission Info

Judge Result