Tenka1 Programmer Contest C - Align

問題ページ

思考過程

• ジグザグにするのがよさそう
• 一番小さい、大きいのを端に置くと損してる
• ジグザグな山みたいなのをつくるのがよさそう
• 一番小さいのを中央に置くか、一番大きいのを中央に置くかで2種類あるのに気をつけながら書くと通った

#include <bits/stdc++.h>
 
using namespace std;
using ll = long long;
// #define int ll
using PII = pair<int, int>;
 
#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
 
template<typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template<typename T> bool IN(T a, T b, T x) { return a<=x&&x<b; }
template<typename T> T ceil(T a, T b) { return a/b + !!(a%b); }
 
template<typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts) { 
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}
template<typename T,typename V> typename enable_if<is_class<T>::value==0>::type
fill_v(T &t, const V &v) { t=v; }
template<typename T,typename V> typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t, const V &v ) { for(auto &e:t) fill_v(e,v); }
 
template<class S,class T>
ostream &operator <<(ostream& out,const pair<S,T>& a){
  out<<'('<<a.first<<','<<a.second<<')'; return out;
}
template<typename T>
istream& operator >> (istream& is, vector<T>& vec){
  for(T& x: vec) {is >> x;} return is;
}
template<class T>
ostream &operator <<(ostream& out,const vector<T>& a){
  out<<'['; for(T i: a) {out<<i<<',';} out<<']'; return out;
}
 
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0}; // DRUL
const int INF = 1<<30;
const ll LLINF = 1LL<<60;
ll MOD = 1000000007;

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

  ll n;
  cin >> n;
  vector<ll> a(n);
  REP(i, n) cin >> a[i];

  ll mid = n/2;
  if(n%2==0) mid--;
  sort(ALL(a));
  vector<ll> v(n);
  v[mid] = a[0];
  for(int i=mid+2, j=1; i<n; i+=2, j+=2) {
    v[i] = a[j];
  }
  for(int i=mid+1, j=n-1; i<n; i+=2, j-=2) {
    v[i] = a[j];
  }
  for(int i=mid-2, j=2; i>=0; i-=2, j+=2) {
    v[i] = a[j];
  }
  for(int i=mid-1, j=n-2; i>=0; i-=2, j-=2) {
    v[i] = a[j];
  }
  ll ret = 0;
  FOR(i, 1, n) ret += abs(v[i]-v[i-1]);
  ll ans = ret;

  reverse(ALL(a));
  v[mid] = a[0];
  for(int i=mid+2; i<n; i+=2) {
    v[i] = a[i-mid-1];
  }
  for(int i=mid+1, j=n-1; i<n; i+=2, j-=2) {
    v[i] = a[j];
  }
  for(int i=mid-2, j=2; i>=0; i-=2, j+=2) {
    v[i] = a[j];
  }
  for(int i=mid-1, j=n-2; i>=0; i-=2, j-=2) {
    v[i] = a[j];
  }
  ret = 0;
  FOR(i, 1, n) ret += abs(v[i]-v[i-1]);
  chmax(ans, ret);

  cout << ans << endl;

  return 0;
}