제출 #143531

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
143531		popovicirobert	Mousetrap (CEOI17_mousetrap)	C++14	100 / 100	1006 ms	178596 KiB

mousetrap

#include <bits/stdc++.h>
#define lsb(x) (x & (-x))
#define ll long long
#define ull unsigned long long



/*const int MOD = ;

inline int lgput(int a, int b) {
    int ans = 1;
    while(b > 0) {
        if(b & 1) ans = (1LL * ans * a) % MOD;
        b >>= 1;
        a = (1LL * a * a) % MOD;
    }
    return ans;
}

inline void mod(int &x) {
    if(x >= MOD)
        x -= MOD;
}

inline void add(int &x, int y) {
    x += y;
    mod(x);
}

inline void sub(int &x, int y) {
    x += MOD - y;
    mod(x);
}

inline void mul(int &x, int y) {
    x = (1LL * x * y) % MOD;
}

inline int inv(int x) {
    return lgput(x, MOD - 2);
}*/

/*int fact[], invfact[];

inline void prec(int n) {
    fact[0] = 1;
    for(int i = 1; i <= n; i++) {
        fact[i] = (1LL * fact[i - 1] * i) % MOD;
    }
    invfact[n] = lgput(fact[n], MOD - 2);
    for(int i = n - 1; i >= 0; i--) {
        invfact[i] = (1LL * invfact[i + 1] * (i + 1)) % MOD;
    }
}

inline int comb(int n, int k) {
    if(n < k) return 0;
    return (1LL * fact[n] * (1LL * invfact[k] * invfact[n - k] % MOD)) % MOD;
}*/

using namespace std;

const int MAXN = (int) 1e6;

vector <int> g[MAXN + 1];
int father[MAXN + 1];

inline void combine(pair <int, int> &mx, int cur) {
    if(mx.first < cur) {
        mx.second = mx.first;
        mx.first = cur;
    }
    else if(mx.second < cur) {
        mx.second = cur;
    }
}

int dp[MAXN + 1];

void go(int nod, int par) {
    father[nod] = par;
    if(par != 0) {
        g[nod].erase(find(g[nod].begin(), g[nod].end(), par));
    }
    pair <int, int> mx = {0, 0};
    for(auto it : g[nod]) {
        go(it, nod);
        combine(mx, dp[it]);
    }
    dp[nod] = mx.second + g[nod].size();
}

int main() {
#if 0
    ifstream cin("A.in");
    ofstream cout("A.out");
#endif
    int i, n, t, m;
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    cin >> n >> t >> m;

    if(m == t) {
        cout << 0;
        return 0;
    }

    for(i = 1; i < n; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }

    go(t, 0);

    vector <int> anc, sp;
    int nod = m;
    while(nod != t) {
        anc.push_back(nod);
        sp.push_back(0);
        nod = father[nod];
    }

    sp.push_back(0);
    for(i = (int) sp.size() - 2; i >= 0; i--) {
        sp[i] = sp[i + 1] + (int) g[anc[i]].size() - (i > 0);
    }

    auto check = [&](int X) -> bool {
        int cnt = 0;
        for(i = 0; i < anc.size(); i++) {
            int last = (i == 0 ? 0 : anc[i - 1]), num = 0;
            for(auto it : g[anc[i]]) {
                if(last == it) continue;

                if(cnt + dp[it] + sp[i] - num > X) {
                    cnt++, num++;
                }
                if(cnt > i + 1) {
                    return 0;
                }
            }
        }
        return cnt <= X;
    };

    int res = -1;
    for(int step = 1 << 20; step; step >>= 1) {
        if(check(res + step) == 0) {
            res += step;
        }
    }

    cout << res + 1;

    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

mousetrap.cpp: In lambda function:
mousetrap.cpp:133:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(i = 0; i < anc.size(); i++) {
                    ~~^~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 25 / 25
• Subtask 3: 20 / 20
• Subtask 4: 35 / 35