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Submission #320678

# Submission time Handle Problem Language Result Execution time Memory
320678 2020-11-09T13:53:14 Z phathnv Mousetrap (CEOI17_mousetrap) C++11
100 / 100
 3202 ms 159652 KB 
#include <bits/stdc++.h>

#define mp make_pair
#define X first
#define Y second

using namespace std;

typedef long long ll;
typedef pair <int, int> ii;

const int N = 1e6 + 1;

int n, t, m;
vector <int> adj[N];

int dp[N], par[N], h[N], b[N];
bool inPath[N];
vector <ii> d;

void readInput(){
    scanf("%d %d %d", &n, &t, &m);
    for(int i = 1; i < n; i++){
        int u, v;
        scanf("%d %d", &u, &v);
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
}

void dfs(int u, int p){
    for(int v : adj[u])
        if (v != p){
            par[v] = u;
            h[v] = h[u] + 1;
            dfs(v, u);
            inPath[u] |= inPath[v];
        }
}

void calcDp(int u, int p){
    if (inPath[u]){
        dp[u] = -1;
        for(int v : adj[u])
            if (v != p)
                calcDp(v, u);
        return;
    }

    dp[u] = 0;
    int nChild = 0, max1 = 0, max2 = 0;
    for(int v : adj[u])
        if (v != p && !inPath[v]){
            nChild++;
            calcDp(v, u);
            max2 = max(max2, dp[v]);
            if (max1 < max2)
                swap(max1, max2);
        }
    dp[u] = max2 + nChild;
}

void prepare(){
    inPath[m] = 1;
    dfs(t, -1);
    inPath[m] = 0;
    calcDp(t, -1);
    inPath[m] = 1;

    int u = -1, cnt = 0;
    for(int v : adj[t])
        if (v != par[t] && inPath[v])
            u = v;
    while (u != -1){
        for(int v : adj[u])
            if (v != par[u] && !inPath[v])
                cnt++;
        for(int v : adj[u])
            if (v != par[u] && !inPath[v])
                d.push_back(mp(h[m] - h[u] + 1, dp[v] + cnt));
        int nxt = -1;
        for(int v : adj[u])
            if (v != par[u] && inPath[v])
                nxt = v;
        u = nxt;
    }

    sort(d.begin(), d.end(), [](const ii &a, const ii &b){
            if (a.X != b.X)
                return a.X < b.X;
            return a.Y > b.Y;
         });
}

bool check(int x){
    int blocked = 0, cnt = 0, cur = 0;
    for(ii p : d){
        if (p.X != cur){
            blocked += cnt;
            cur = p.X;
            cnt = 0;
        }
        if (p.Y + blocked > x){
            if (blocked + cnt < min(x, p.X))
                cnt++;
            else
                return 0;
        }
    }
    return 1;
}

void solve(){
    cerr << "d: " << endl;
    for(ii p : d)
        cerr << p.X << ' ' << p.Y << endl;
    int l = 0, r = n - 1, res = -1;
    while (l <= r){
        int mid = (l + r) >> 1;
        if (check(mid)){
            res = mid;
            r = mid - 1;
        } else {
            l = mid + 1;
        }
    }

    printf("%d", res);
}

int main(){
    readInput();
    prepare();
    solve();
    return 0;
}

Compilation message

mousetrap.cpp: In function 'void readInput()':
mousetrap.cpp:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |     scanf("%d %d %d", &n, &t, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:25:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   25 |         scanf("%d %d", &u, &v);
      |         ~~~~~^~~~~~~~~~~~~~~~~

Subtask #1
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 16 ms 23788 KB Output is correct
3 Correct 16 ms 23788 KB Output is correct
4 Correct 18 ms 23792 KB Output is correct
5 Correct 17 ms 23916 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 16 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 452 ms 80764 KB Output is correct
2 Correct 370 ms 75236 KB Output is correct
3 Correct 1082 ms 82344 KB Output is correct
4 Correct 512 ms 52984 KB Output is correct
5 Correct 1082 ms 82276 KB Output is correct
6 Correct 1092 ms 82148 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 16 ms 23788 KB Output is correct
3 Correct 16 ms 23788 KB Output is correct
4 Correct 18 ms 23792 KB Output is correct
5 Correct 17 ms 23916 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 16 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct
11 Correct 16 ms 23788 KB Output is correct
12 Correct 16 ms 23916 KB Output is correct
13 Correct 16 ms 23916 KB Output is correct
14 Correct 18 ms 23952 KB Output is correct
15 Correct 16 ms 23916 KB Output is correct
16 Correct 17 ms 23916 KB Output is correct
17 Correct 17 ms 23916 KB Output is correct
18 Correct 16 ms 23916 KB Output is correct
19 Correct 16 ms 23916 KB Output is correct
20 Correct 18 ms 23916 KB Output is correct
21 Correct 18 ms 23916 KB Output is correct
22 Correct 22 ms 23916 KB Output is correct

Subtask #4
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 16 ms 23788 KB Output is correct
3 Correct 16 ms 23788 KB Output is correct
4 Correct 18 ms 23792 KB Output is correct
5 Correct 17 ms 23916 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 16 ms 23788 KB Output is correct
9 Correct 15 ms 23788 KB Output is correct
10 Correct 15 ms 23788 KB Output is correct
11 Correct 452 ms 80764 KB Output is correct
12 Correct 370 ms 75236 KB Output is correct
13 Correct 1082 ms 82344 KB Output is correct
14 Correct 512 ms 52984 KB Output is correct
15 Correct 1082 ms 82276 KB Output is correct
16 Correct 1092 ms 82148 KB Output is correct
17 Correct 16 ms 23788 KB Output is correct
18 Correct 16 ms 23916 KB Output is correct
19 Correct 16 ms 23916 KB Output is correct
20 Correct 18 ms 23952 KB Output is correct
21 Correct 16 ms 23916 KB Output is correct
22 Correct 17 ms 23916 KB Output is correct
23 Correct 17 ms 23916 KB Output is correct
24 Correct 16 ms 23916 KB Output is correct
25 Correct 16 ms 23916 KB Output is correct
26 Correct 18 ms 23916 KB Output is correct
27 Correct 18 ms 23916 KB Output is correct
28 Correct 22 ms 23916 KB Output is correct
29 Correct 15 ms 23788 KB Output is correct
30 Correct 411 ms 80936 KB Output is correct
31 Correct 405 ms 80868 KB Output is correct
32 Correct 479 ms 159652 KB Output is correct
33 Correct 554 ms 159644 KB Output is correct
34 Correct 1157 ms 82452 KB Output is correct
35 Correct 1096 ms 82320 KB Output is correct
36 Correct 3202 ms 94764 KB Output is correct
37 Correct 3162 ms 94792 KB Output is correct
38 Correct 1775 ms 94296 KB Output is correct
39 Correct 1803 ms 94200 KB Output is correct
40 Correct 1833 ms 94332 KB Output is correct