Submission #376304

#	Time	Username	Problem	Language	Result	Execution time	Memory
376304		dantoh000	Papričice (COCI20_papricice)	C++14	110 / 110	253 ms	30568 KiB

papricice

#include <bits/stdc++.h>
using namespace std;
int n;
vector<int> G[200005];
int p[200005];
int col[200005];
int sz[200005];
int root;
void dfs(int u){
    sz[u] = 1;
    for (auto v : G[u]){
        if (v == p[u]) continue;
        p[v] = u;
        dfs(v);
        sz[u] += sz[v];
    }
}
int findcentroid(int u){
    for (auto v : G[u]){
        if (v == p[u]) continue;
        if (sz[v] > n/2) return findcentroid(v);
    }
    return u;
}
vector<int> COL[200005];
set<int> rest;
set<int> hmm;
int curcol = 1;
void dfs2(int u){
    sz[u] = 1;
    COL[col[u]].push_back(u);
    for (auto v : G[u]){
        if (p[u] == v) continue;
        //printf("%d -> %d\n",u,v);
        p[v] = u;
        if (u == root){
            col[v] = curcol++;
        }
        else col[v] = col[u];
        dfs2(v);
        sz[u] += sz[v];
    }
}
int ans;
void process(int a, int b, int c){
    ans = min(ans, max(a,max(b,c)) - min(a,min(b,c)));
}
int main(){
    scanf("%d",&n);
    ans = n;
    for (int i = 0; i < n-1; i++){
        int x,y;
        scanf("%d%d",&x,&y);
        G[x].push_back(y);
        G[y].push_back(x);
    }
    p[1] = -1;
    dfs(1);
    root = findcentroid(1);
    for (int i = 1; i <= n; i++) p[i] = -1;
    col[root] = 0;
    dfs2(root);
    //printf("centroid is %d\n",root);
    for (int c = 1; c <= curcol; c++){
        for (auto u : COL[c]){
            //printf("col %d: %d\n",c,u);
        }
        for (auto u : COL[c]){
            hmm.insert(sz[u]);
        }
        for (auto u : COL[c]){
            int a = sz[u];
            int bad = n-a;
            ///search inside
            auto it = hmm.lower_bound(a+bad/2);
            if (it != hmm.end()){
                int b = *it - a;
                int c = n-a-b;
                process(a,b,c);
            }
            it = hmm.lower_bound(a+bad/2+1);
            if (it != hmm.end()){
                int b = *it - a;
                int c = n-a-b;
                process(a,b,c);
            }
            it = hmm.upper_bound(a+bad/2);
            if (it != hmm.begin()){
                it--;
                int b = *it - a;
                int c = n-a-b;
                process(a,b,c);
            }
            it = hmm.upper_bound(a+bad/2-1);
            if (it != hmm.begin()){
                it--;
                int b = *it - a;
                int c = n-a-b;
                process(a,b,c);
            }
            /// search outside
            it = rest.lower_bound(bad/2);
            if (it != rest.end()){
                int b = *it;
                int c = n-a-b;
                process(a,b,c);
            }
            it = rest.lower_bound(bad/2+1);
            if (it != rest.end()){
                int b = *it;
                int c = n-a-b;
                process(a,b,c);
            }
            it = rest.upper_bound(bad/2);
            if (it != rest.begin()){
                it--;
                int b = *it;
                int c = n-a-b;
                process(a,b,c);
            }
            it = rest.upper_bound(bad/2-1);
            if (it != rest.begin()){
                it--;
                int b = *it;
                int c = n-a-b;
                process(a,b,c);
            }
            //printf("after checking %d, ans = %d\n",u,ans);
        }
        for (auto u : COL[c]){
            rest.insert(sz[u]);
        }
        hmm.clear();
    }

    printf("%d",ans);
}

Compilation message (stderr)

papricice.cpp: In function 'int main()':
papricice.cpp:65:19: warning: unused variable 'u' [-Wunused-variable]
   65 |         for (auto u : COL[c]){
      |                   ^
papricice.cpp:49:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   49 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
papricice.cpp:53:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   53 |         scanf("%d%d",&x,&y);
      |         ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 35 / 35
• Subtask 3: 60 / 60