Submission #1006103

#	Time	Username	Problem	Language	Result	Execution time	Memory
1006103		crafticat	Wells (CEOI21_wells)	C++17	0 / 100	4 ms	452 KiB

wells

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using pi = pair<int,int>;
using pl = pair<ll,ll>;

#define temp(T) template<class T>
temp(T) using V = vector<T>;
using vi = V<int>;
using vl = V<ll>;
using vvi = V<vi>;
using vpi = V<pi>;
using vb = V<bool>;

#define sz(x) x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sor(x) sort(all(x))
#define rsz resize
#define ins insert
#define pb push_back
#define eb emplace_back

#define lb lower_bound
#define ub upper_bound

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define rep(a) F0R(_,a)
#define each(a,x) for (auto& a: x)

using str = string;

const int MOD = 1e9 + 7;
const ll BIG = 1e18;
const int INF = 1e9 + 2;

temp(T) bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; } // set a = min(a,b)
temp(T) bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; } // set a = max(a,b)

void unsyncIO() { cin.tie(0)->sync_with_stdio(0); }
// FILE I/O
void setIn(str s) { freopen(s.c_str(),"r",stdin); }
void setOut(str s) { freopen(s.c_str(),"w",stdout); }
void setIO(str s = "") {
    unsyncIO();
    if (sz(s)) setIn(s+".in"), setOut(s+".out"); // for USACO
}

#define read(x) int x; cin >> x;

temp(T) void pr(T x) {
    cout << to_string(x);
}
temp(T) void prln(T x) {
    cout << (x) << "\n";
}


vi readV(int n) {
    vi input(n);
    F0R(i,n)
        cin >> input[i];
    return input;
}

int rand(int a, int b) {
    return a + rand() % (b - a + 1);
}

#define gen(x,a,b) int x = rand(a,b)

vi genArr(int n, int a, int b) {
    vi generated(n);
    F0R(i,n) {
        generated[i] = rand(a,b);
    }
    return generated;
}

vvi readTree(int n) {
    vvi g(n + 1);
    F0R(i,n - 1) {
        read(a); read(b);
        g[a].pb(b);
        g[b].pb(a);
    }
    return g;
}

vvi genTree(int n) {
    vvi g(n + 1);
    F0R(i,n) {
        gen(p,0,i);
        g[p].pb(i + 1);
        g[i + 1].pb(p);
    }

    return g;
}

vb imp;
vvi g;
vi cnt;
int k;

int isImp(int x, int p) {
    int f = 0;
    each(child,g[x]) {
        if (child == p) continue;
        ckmax(f, isImp(child,x) + 1);
    }
    if (f <= k / 2) imp[x] = false;
    return f;
}
int countSpec(int x, int p, int h) {
    if (h >= k / 2) return 1;
    int ans = 0;
    each(child,g[x]) {
        if (child == p) continue;
        ans += countSpec(child,x,h + 1);
    }
    return ans;
}

bool pos(int x, int p, int h) {
    int cnt0 = countSpec(x,p,0);
    if (h % k == k / 2 && cnt0 > 1)
        return false;
    each(child,g[x]) {
        if (child == p) continue;
        if (!pos(child,x,h + 1)) return false;
    }
    return true;
}

int main() {
    read(n);
    cin >> k;
    g = readTree(n);

    imp.rsz(n + 1,true);
    FOR(i,1,n) {
        isImp(i,-1);
    }
    cnt.rsz(n + 1);
    FOR(i,1,n) {
        each(child, g[i])
            if (imp[child]) cnt[i]++;
    }

    bool ans = false;
    int alive = 0;
    FOR(i,1,n) {
        if (!imp[i]) continue;
        alive++;
        if (pos(i,-1,0)) {
            ans = true;
        }
    }
    if (alive == 0) ans = true;
    prln(ans ? "YES" : "NO");
    pr(0);

    return 0;
}

Compilation message (stderr)

wells.cpp: In function 'void setIn(str)':
wells.cpp:49:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 | void setIn(str s) { freopen(s.c_str(),"r",stdin); }
      |                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
wells.cpp: In function 'void setOut(str)':
wells.cpp:50:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 | void setOut(str s) { freopen(s.c_str(),"w",stdout); }
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 30