Language: C++

#include <iostream>
#include <array>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <algorithm>
#include <math.h>
#include <string>
#include <climits>
#include <assert.h>
#include <iomanip>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <functional>
#include <fstream>

#define SIZE(x) int(x.size())
#define FOR(i,a,n) for(int i=(a);i<(n); ++i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define IS_BIT_ON(bit, i) (bit & (1 << i))
#define BIT_ON(bit, i) (bit |= (1 << i))
#define BIT_OFF(bit, i) (bit &= ~(1 << i))
#define BIT_COUNT(bit) (__builtin_popcount(bit))

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
void print() { std::cout << std::endl; }
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) { std::cout << head; if (sizeof...(tail) != 0) {std::cout << " ";} print(std::forward<Tail>(tail)...); }
template <class T> void print(std::vector<T> &v) {for (auto& a : v) { std::cout << a; if (&a != &v.back()) {std::cout << " ";} }std::cout << std::endl;}
template <class T> void print(std::vector<std::vector<T>> &vv) { for (auto& v : vv) { print(v); }}
void debug() { std::cerr << std::endl; }
template <class Head, class... Tail> void debug(Head&& head, Tail&&... tail) { std::cerr << head; if (sizeof...(tail) != 0) {std::cerr << " ";} print(std::forward<Tail>(tail)...); }
template <class T> void debug(std::vector<T> &v) {for (auto& a : v) { std::cerr << a; if (&a != &v.back()) {std::cerr << " ";} }std::cerr << std::endl;}
template <class T> void debug(std::vector<std::vector<T>> &vv) { for (auto& v : vv) { print(v); }}
inline bool inside(long long y, long long x, long long H, long long W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}

long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

bool is_power_of_two(long long x) {
    return !(x & (x - 1));
}

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

long long gcd(std::vector<long long> &v) {
    long long ans = v[0];
    for (int i = 1; i < (int)v.size(); ++i) {
        ans = gcd(ans, v[i]);
    }
    return ans;
}

long long lcm(long long a, long long b) {
    long long g = gcd(a, b);
    return a / g * b;
}

const int INF = 1u << 30u;
const long long LINF = 1ull << 58u;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};
const std::vector<int> dy4 = {0, 1, 0, -1}, dx4 = {1, 0, -1, 0};
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;



template<class T=double> class vec {
public:
    T x;
    T y;
    const double eps = 1e-9;

    vec() : x(0), y(0) {

    }

    vec(T x, T y) : x(x), y(y) {

    }

    vec &operator=(const vec &v) {
        x = v.x;
        y = v.y;
        return *this;
    }

    vec &operator+=(const vec &v) {
        x += v.x;
        y += v.y;
        return *this;
    }

    vec operator+(const vec &v) const {
        return vec(*this) += v;
    }

    vec &operator-=(const vec &v) {
        x -= v.x;
        y -= v.y;
        return *this;
    }

    vec operator-(const vec &v) const {
        return vec(*this) -= v;
    }

    vec &operator*=(double s) {
        x *= s;
        y *= s;
        return *this;
    }

    vec operator*(double s) const {
        return vec(*this) *= s;
    }

    vec &operator/=(double s) {
        x /= s;
        y /= s;
        return *this;
    }

    vec operator/(double s) const {
        return vec(*this) /= s;
    }

    T dot(const vec &v) const {
        return x * v.x + y * v.y;
    }

    T cross(const vec &v) const {
        return x * v.y - v.x * y;
    }

    T norm2() const {
        return x * x + y * y;
    }

    double norm() const {
        return sqrt(norm2());
    }

    // 象限
    int orthant() const {
        if (abs(x) < eps and abs(y) < eps) {
            return 0;
        }
        if (y > 0) {
            return x > 0 ? 1 : 2;
        }
        else {
            return x < 0 ? 3 : 4;
        }
    }

    // 偏角ソート用(反時計回りにソート)
    bool operator<(const vec &v) const {
        int o = orthant(), vo = v.orthant();
        if (o != vo) {
            return o < vo;
        }
        return cross(v) > 0;
    }
};


template<typename T>class CumulativeSum {
public:
    std::vector<T> memo1;               // 1次元用の累積和表
    std::vector<std::vector<T>> memo2;  // 2次元用の累積和表

    CumulativeSum() {}

    void build(const std::vector<T> &line) {
        this->memo1.assign(line.size() + 1, 0);

        for (int i = 0; i < line.size(); ++i) {
            this->memo1[i + 1] = this->memo1[i] + line[i];
        }
    }

    // 2次元の累積和表を作成
    void build(const std::vector<std::vector<T>> &board) {
        int height = board.size();
        int width = board[0].size();
        this->memo2.assign(height + 1, std::vector<T>(width + 1, 0));

        for (int y = 0; y < height; ++y) {
            for (int x = 0; x < width; ++x) {
                memo2[y + 1][x + 1] = board[y][x] + memo2[y + 1][x];
            }
            for (int x = 0; x < width; ++x) {
                memo2[y + 1][x + 1] += memo2[y][x + 1];
            }
        }
    }

    T sum(int left, int right) {
        return this->memo1[right] - this->memo1[left];
    }

    /*
    (y1, x1)から(y2, x2)の合計を返す．(y2, x2)は含まない
    座標はmemoを作成したboard準拠
    (ex, sum(0, 0, 2, 2)なら(0, 0), (0, 1), (1, 0), (1, 1)の合計を返す)
    */
    T sum(int y1, int x1, int y2, int x2) {
        return this->memo2[y2][x2] - this->memo2[y2][x1] - this->memo2[y1][x2] + this->memo2[y1][x1];
    }
};

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

    int N;
    cin >> N;
    vector<vec> v(N);
    FOR(i, 0, N) {
        LL X, Y;
        cin >> X >> Y;
        v[i] = vec(X, Y);
    }
    sort(ALL(v));

    auto X = make_v<LL>(N * 3);
    auto Y = make_v<LL>(N * 3);
    FOR(i, 0, N) {
        X[i] = X[i + N] = X[i + 2 * N] = v[i].x;
        Y[i] = Y[i + N] = Y[i + 2 * N] = v[i].y;
    }

    CumulativeSum<LL> cs_x; cs_x.build(X);
    CumulativeSum<LL> cs_y; cs_y.build(Y);
    LL ans = 0;
    FOR(i, 0, N) {
        FOR(j, i + 1, i + N + 1) {
            LL x = cs_x.sum(i, j);
            LL y = cs_y.sum(i, j);
            chmax(ans, x * x + y * y);
        }
    }

    cout << fixed << setprecision(11) << sqrt(ans) << endl;

    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:250:15: error: type/value mismatch at argument 1 in template parameter list for 'template<class _Tp, class _Alloc> class std::vector'
  250 |     vector<vec> v(N);
      |               ^
a.cc:250:15: note:   expected a type, got 'vec'
a.cc:250:15: error: template argument 2 is invalid
a.cc:254:10: error: invalid types 'int[int]' for array subscript
  254 |         v[i] = vec(X, Y);
      |          ^
a.cc:24:20: error: request for member 'begin' in 'v', which is of non-class type 'int'
   24 | #define ALL(c) (c).begin(), (c).end()
      |                    ^~~~~
a.cc:256:10: note: in expansion of macro 'ALL'
  256 |     sort(ALL(v));
      |          ^~~
a.cc:24:33: error: request for member 'end' in 'v', which is of non-class type 'int'
   24 | #define ALL(c) (c).begin(), (c).end()
      |                                 ^~~
a.cc:256:10: note: in expansion of macro 'ALL'
  256 |     sort(ALL(v));
      |          ^~~
a.cc:261:43: error: invalid types 'int[int]' for array subscript
  261 |         X[i] = X[i + N] = X[i + 2 * N] = v[i].x;
      |                                           ^
a.cc:262:43: error: invalid types 'int[int]' for array subscript
  262 |         Y[i] = Y[i + N] = Y[i + 2 * N] = v[i].y;
      |                                           ^