Submission #1037804

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037804		Forested	Simurgh (IOI17_simurgh)	C++17	51 / 100	91 ms	3272 KiB

simurgh

#include <bits/stdc++.h>
using namespace std;
using i32 = int;
using i64 = long long;
template <typename T>
using V = vector<T>;
template <typename T>
using VV = V<V<T>>;
template <typename T>
using VVV = V<VV<T>>;
template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}
#define OVERRIDE4(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, l, r) for (i32 i = (i32)(l); i < (i32)(r); ++i)
#define REP(...) OVERRIDE4(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER2(i, n) for (i32 i = (i32)(n)-1; i >= 0; --i)
#define PER3(i, l, r) for (i32 i = (i32)(r)-1; i >= (i32)(l); --i)
#define PER(...) OVERRIDE4(__VA_ARGS__, PER3, PER2)(__VA_ARGS__)
#define LEN(x) (i32) size(x)
#define ALL(x) begin(x), end(x)

void dbg(i32 x) { cerr << x; }
void dbg(i64 x) { cerr << x; }
template <typename T, typename U>
void dbg(pair<T, U> p) {
    cerr << "(";
    dbg(p.first);
    cerr << ", ";
    dbg(p.second);
    cerr << ")";
}
template <typename T>
void dbg(V<T> arr) {
    cerr << "[";
    REP(i, LEN(arr)) {
        if (i) {
            cerr << ", ";
        }
        dbg(arr[i]);
    }
    cerr << "]";
}
void debug() { cerr << '\n'; }
template <typename Head, typename... Tail>
void debug(Head head, Tail... tail) {
    dbg(head);
    cerr << ", ";
    debug(tail...);
}
#ifdef DEBUGF
#define DBG(...)                       \
    do {                               \
        cerr << #__VA_ARGS__ << " : "; \
        debug(__VA_ARGS__);            \
    } while (false)
#else
#define DBG(...) (void)0
#endif

#include "simurgh.h"

V<i32> subtask_3(i32 n, V<i32> u, V<i32> v) {
    struct Edge {
        i32 to, id;
    };
    i32 m = LEN(u);
    VV<Edge> g(n);
    REP(i, m) {
        g[u[i]].emplace_back(Edge{v[i], i});
        g[v[i]].emplace_back(Edge{u[i], i});
    }
    i32 root = 0;
    V<i32> par(n, -1), pid(n, -1), dep(n, -1);
    {
        queue<i32> que;
        que.push(root);
        dep[root] = 0;
        while (!que.empty()) {
            i32 v = que.front();
            que.pop();
            for (const Edge &e : g[v]) {
                if (dep[e.to] == -1) {
                    par[e.to] = v;
                    pid[e.to] = e.id;
                    dep[e.to] = dep[v] + 1;
                    que.push(e.to);
                }
            }
        }
    }
    V<i32> tree;
    REP(i, n) {
        if (pid[i] != -1) {
            tree.push_back(pid[i]);
        }
    }
    i32 base = count_common_roads(tree);
    V<i32> con(m, -1);
    REP(i, m) {
        if (count(ALL(tree), i)) {
            continue;
        }
        V<i32> loop;
        {
            i32 x = u[i], y = v[i];
            while (x != y) {
                if (dep[x] < dep[y]) {
                    swap(x, y);
                }
                loop.push_back(pid[x]);
                x = par[x];
            }
        }
        const i32 nil = 998;
        V<i32> diffs(LEN(loop), nil);
        REP(j, LEN(loop)) {
            i32 e = loop[j];
            if (con[e] != -1) {
                continue;
            }
            V<i32> ask = tree;
            ask.erase(find(ALL(ask), e));
            ask.push_back(i);
            diffs[j] = count_common_roads(ask) - base;
        }
        if (auto itr = find(ALL(diffs), nil); itr != end(diffs)) {
            {
                i32 e = loop[itr - begin(diffs)];
                V<i32> ask = tree;
                ask.erase(find(ALL(ask), e));
                ask.push_back(i);
                i32 di = count_common_roads(ask) - base;
                con[i] = di + con[e];
            }
            REP(j, LEN(loop)) {
                i32 e = loop[j];
                if (con[e] != -1) {
                    continue;
                }
                // diffs[j] = con[i] - con[e]
                con[e] = con[i] - diffs[j];
            }
        } else if (count(ALL(diffs), 0) == LEN(diffs)) {
            con[i] = 0;
            REP(j, LEN(diffs)) { con[loop[j]] = 0; }
        } else {
            REP(j, LEN(loop)) {
                if (diffs[j] == 1) {
                    con[i] = 1;
                }
                if (diffs[j] == -1) {
                    con[i] = 0;
                }
            }
            REP(j, LEN(loop)) {
                i32 e = loop[j];
                con[e] = con[i] - diffs[j];
            }
        }
    }
    REP(i, m) {
        if (con[i] == -1) {
            con[i] = 1;
        }
    }
    V<i32> ans;
    REP(i, m) {
        if (con[i] == 1) {
            ans.push_back(i);
        }
    }
    return ans;
}

V<i32> subtask_4(i32 n, V<i32> u, V<i32> v) {
    if (n == 2) {
        return V<i32>({0});
    }
    i32 m = LEN(u);
    VV<i32> eid(n, V<i32>(n, -1));
    REP(i, m) { eid[u[i]][v[i]] = eid[v[i]][u[i]] = i; }
    V<i32> con(m, -1);
    V<i32> inh;
    auto check = [&](i32 r) -> void {
        DBG(r);
        V<i32> star;
        REP(i, n) {
            if (i != r) {
                star.push_back(eid[r][i]);
            }
        }
        i32 base = count_common_roads(star);
        DBG(star, base);
        REP(i, n) {
            if (i == r) {
                continue;
            }
            i32 nx = i + 1;
            if (nx == r) {
                ++nx;
            }
            if (nx == n) {
                nx = 0;
            }
            if (nx == r) {
                ++nx;
            }
            if (nx == n) {
                nx = 0;
            }
            i32 e = eid[i][nx];
            DBG(i, nx, e);
            i32 d0 = 0, d1 = 0;
            {
                V<i32> ask = star;
                ask.erase(find(ALL(ask), eid[r][i]));
                ask.push_back(e);
                d0 = count_common_roads(ask) - base;
            }
            {
                V<i32> ask = star;
                ask.erase(find(ALL(ask), eid[r][nx]));
                ask.push_back(e);
                d1 = count_common_roads(ask) - base;
            }
            if (d0 == 0 && d1 == 0) {
                con[eid[r][i]] = con[eid[r][nx]] = con[e] = 0;
            } else {
                // d0 = con[e] - con[eid[r][i]]
                if (d0 != 0) {
                    con[e] = (d0 + 1) / 2;
                }
                if (d1 != 0) {
                    con[e] = (d1 + 1) / 2;
                }
                con[eid[r][i]] = con[e] - d0;
                con[eid[r][nx]] = con[e] - d1;
            }
        }
        DBG(con);
        inh.clear();
        REP(i, n) {
            if (i != r && con[eid[0][i]] == 1) {
                inh.push_back(i);
            }
        }
        V<i32> rems;
        star.clear();
        REP(i, n) {
            if (i != r && con[eid[r][i]] == 0) {
                rems.push_back(i);
            }
            if (i != r && con[eid[r][i]] == 1) {
                star.push_back(eid[r][i]);
            }
        }
        if (LEN(rems) <= 1) {
            return;
        }
        REP(i, LEN(rems) - 1) {
            i32 v = rems[i];
            i32 l = i + 1;
            while (l < LEN(rems)) {
                i32 ok = LEN(rems), ng = l - 1;
                while (ok - ng > 1) {
                    i32 mid = (ok + ng) / 2;
                    V<i32> ask = star;
                    REP(j, LEN(rems)) {
                        if (!(l <= j && j <= mid)) {
                            ask.push_back(eid[r][rems[j]]);
                        }
                    }
                    REP(j, l, mid + 1) {
                        ask.push_back(eid[v][rems[j]]);
                    }
                    if (count_common_roads(ask) == LEN(star)) {
                        ng = mid;
                    } else {
                        ok = mid;
                    }
                }
                REP(j, l, ok) {
                    con[eid[v][rems[j]]] = 0;
                }
                if (ok == LEN(rems)) {
                    break;
                }
                con[eid[v][rems[ok]]] = 1;
                l = ok + 1;
            }
        }
        DBG(con);
    };
    check(0);
    if (!inh.empty()) {
        check(inh[0]);
    }
    V<i32> ans;
    REP(i, m) {
        if (con[i] == 1) {
            ans.push_back(i);
        }
    }
    if (LEN(ans) != n - 1) {
        assert(false);
    }
    return ans;
}

V<i32> find_roads(i32 n, V<i32> u, V<i32> v) {
    if (LEN(u) == n * (n - 1) / 2) {
        return subtask_4(n, u, v);
    }
    if (n <= 240) {
        return subtask_3(n, u, v);
    }
    assert(false);
}

• Subtask 1: 13 / 13
• Subtask 2: 17 / 17
• Subtask 3: 21 / 21
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30