Language: C++

#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <tuple>
#include <iomanip>
#include <climits>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
//typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < (n); i++)
#define revrep(i, n) for(ll i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);

//const ll INFL = LLONG_MAX;//10^18 = 2^60
const ll INFL = 1LL<<60;
//const int INF = INT_MAX;
const ll INF = 1 << 30;//10^9
//ll MOD = 1000000007;
ll MOD = 998244353;

vector<ll> dy = {0, 1, 0, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, 0, -1, 0, 1, -1, 1, -1, 0};

void pres(double A, ll x = 20){cout << fixed << setprecision(x) << A << endl;}
void BinarySay(ll x, ll y = 60){rep(i, y) cout << (x>>(y-1-i) & 1); cout << endl;}
ll cnt_bit(ll x){return __builtin_popcountll(x);}

ll pow_long(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2) res *= x;
    x *= x; k /= 2;
  }
  return res;
}

ll pow_mod(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2){
      res *= x; res %= MOD;
    }
    x *= x; x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x){return pow_mod(x, MOD - 2);};

ll gcd(ll a, ll b){
    if(b == 0) return a;
    return gcd(b, a % b);
}

ll lcm(ll x, ll y){
  ll res = x / gcd(x, y);
  res *= y;
  return res;
};


/*
//コンビネーション
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
//facはn!,finvは1/n!
//invは逆元
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAXcomb; i++){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll comb(int n, int k){
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] % MOD * finv[n-k] % MOD;
}

const int MAXkai = 200010;
ll kai_memo[MAXkai];
ll kai(ll N){
  if(kai_memo[N] != 0) return kai_memo[N];
  if(N <= 1) return 1;
  return kai_memo[N] = N * kai(N-1) % MOD;
}
*/

using CHT_TYPE = ll;
class ConvexHullTrickDynamic {
private:
	// 直線 **************************************************************
	struct Line {
		CHT_TYPE a, b; // y = ax + b
		mutable function<const Line*()> getSuc; // 次の直線へのポインタ (ソートで用いる)

		bool operator<(const Line& rhs) const {
			// 取得クエリでは次の直線との差分でソート
			if (rhs.b == IS_QUERY) {
				const Line* suc = getSuc();
				if (suc == nullptr) return false;
				const CHT_TYPE& x = rhs.a;
				return (suc->a - a)*x + suc->b - b > 0;
			}
			if (b == IS_QUERY) {
				const Line* suc = rhs.getSuc();
				if (suc == nullptr) return true;
				const CHT_TYPE& x = a;
				return (suc->a - rhs.a)*x + suc->b - rhs.b < 0;
			}

			// 通常の直線どうしは傾きソート
			return a < rhs.a;
		}
	};

	// 直線集合 **********************************************************
	class LinesSet : public multiset<Line> {
	private:
		// true -> 最小値クエリ, false -> 最大値クエリ
		bool flagMin;

	public:
		// コンストラクタ ( 第一引数falseで最大値クエリ,デフォルトで最小値クエリ )
		LinesSet(bool flagMin = true) : flagMin(flagMin) {};

		// 直線lが不必要であるかどうか
		inline bool isBad(iterator l) {
			const auto&& nel = next(l);
			if (l == begin()) { // lが傾き最小のとき
				if (nel == end()) return false; // lしかないなら必要
				return l->a == nel->a && l->b <= nel->b;
			}
			else {
				const auto&& prl = prev(l);
				if (nel == end()) return l->a == prl->a && l->b <= prl->b;
				return (prl->b - l->b) * (nel->a - l->a) >= (nel->b - l->b) * (prl->a - l->a);
			}
		}

		// 直線y=ax+bを追加する
		inline void add(CHT_TYPE a, CHT_TYPE b) {
			if (flagMin) a = -a, b = -b;
			auto&& it = insert({a, b});
			it->getSuc = [=] { return (next(it) == end() ? nullptr : &*next(it)); };
			if (isBad(it)) { erase(it); return; }
			while (next(it) != end() && isBad(next(it))) erase(next(it));
			while (it != begin() && isBad(prev(it))) erase(prev(it));
		}

		// 直線群の中でxの時に最小(最大)となる値を返す
		inline CHT_TYPE get(CHT_TYPE x) {
			auto&& l = *lower_bound(Line{x, IS_QUERY});
			if (flagMin) return -l.a * x - l.b;
			else return l.a * x + l.b;
		}
	};

	static const CHT_TYPE IS_QUERY = numeric_limits<CHT_TYPE>::lowest();
	LinesSet linesSet;

public:
	// コンストラクタ ( 第一引数falseで最大値クエリ,デフォルトで最小値クエリ )
	ConvexHullTrickDynamic(bool flagMin = true) : linesSet(flagMin) {}
	// 直線y=ax+bを追加する
	inline void add(CHT_TYPE a, CHT_TYPE b) { linesSet.add(a, b); }
	// あるxのときの直線集合での最小値を求める
	inline CHT_TYPE get(CHT_TYPE x) { return linesSet.get(x); }
};

ll N, C;
ll h[200010];
ll dp[200010];
void solve(){
  ConvexHullTrickDynamic cht(true);
  cin >> N >> C;
  rep(i, N) cin >> h[i];
  revrep(i, N) h[i] -= h[0];
  cht.add(-2*h[0], dp[0] + h[0] * h[0]);
  for(ll i = 1; i < N; i++){
    ll m = cht.get(h[i]);
    dp[i] = C + m + h[i] * h[i];
    cht.add(-2*h[i], dp[i] + h[i] * h[i]);
  }
  cout << dp[N-1] << endl;
}

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


Compiler output:
a.cc:116:25: error: 'function' does not name a type; did you mean 'union'?
  116 |                 mutable function<const Line*()> getSuc; // 次の直線へのポインタ (ソートで用いる)
      |                         ^~~~~~~~
      |                         union
a.cc: In member function 'bool ConvexHullTrickDynamic::Line::operator<(const ConvexHullTrickDynamic::Line&) const':
a.cc:121:51: error: 'getSuc' was not declared in this scope; did you mean 'getwc'?
  121 |                                 const Line* suc = getSuc();
      |                                                   ^~~~~~
      |                                                   getwc
a.cc:127:55: error: 'const struct ConvexHullTrickDynamic::Line' has no member named 'getSuc'
  127 |                                 const Line* suc = rhs.getSuc();
      |                                                       ^~~~~~
a.cc: In member function 'void ConvexHullTrickDynamic::LinesSet::add(CHT_TYPE, CHT_TYPE)':
a.cc:166:29: error: 'const struct ConvexHullTrickDynamic::Line' has no member named 'getSuc'
  166 |                         it->getSuc = [=] { return (next(it) == end() ? nullptr : &*next(it)); };
      |                             ^~~~~~