제출 #534333

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
534333		79brue	Mergers (JOI19_mergers)	C++14	100 / 100	1190 ms	155608 KiB

mergers

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

struct UnionFind{
    int par[500002];

    void init(int n){
        for(int i=1; i<=n; i++) par[i] = i;
    }

    int find(int x){
        return x==par[x] ? x : (par[x] = find(par[x]));
    }

    void merge(int x, int y){
        x = find(x), y = find(y);
        par[x] = y;
    }
} dsu;

int n, k;
int arr[500002];
vector<int> link[500002];
int deg[500002], leafCnt;

int in[500002], inCnt;
int par[500002], depth[500002];
int LCADB[500002][20];
vector<int> vec[500002];
int sum[500002];

void dfs(int x, int p=-1){
    in[x] = ++inCnt;
    vec[arr[x]].push_back(x);

    for(auto y: link[x]){
        if(y == p) continue;
        par[y] = LCADB[y][0] = x;
        depth[y] = depth[x]+1;
        dfs(y, x);
    }
}

void dfs2(int x, int p=-1){
    for(auto y: link[x]){
        if(y == p) continue;
        dfs2(y, x);
        sum[in[x]] += sum[in[y]];
    }
    if(sum[in[x]]){
        dsu.merge(x, p);
    }
}

int getLCA(int x, int y){
    if(depth[x] < depth[y]) swap(x, y);
    for(int d=0; d<20; d++) if((depth[x]-depth[y])&(1<<d)) x=LCADB[x][d];
    if(x==y) return x;
    for(int d=19; d>=0; d--) if(LCADB[x][d] != LCADB[y][d]) x = LCADB[x][d], y = LCADB[y][d];
    return par[x];
}

int main(){
    scanf("%d %d", &n, &k);
    dsu.init(n);
    for(int i=1; i<n; i++){
        int x, y;
        scanf("%d %d", &x, &y);
        link[x].push_back(y);
        link[y].push_back(x);
    }
    for(int i=1; i<=n; i++) scanf("%d", &arr[i]);

    dfs(1);
    for(int d=1; d<20; d++) for(int i=1; i<=n; i++) LCADB[i][d] = LCADB[LCADB[i][d-1]][d-1];

    for(int i=1; i<=k; i++){
        sort(vec[i].begin(), vec[i].end(), [&](int x, int y){
            return in[x] < in[y];
        });
        if(!vec[i].empty()) vec[i].push_back(vec[i][0]);
        for(int j=0; j<(int)vec[i].size()-1; j++){
            int x = vec[i][j], y = vec[i][j+1], z = getLCA(x, y);
            sum[in[x]]++, sum[in[y]]++, sum[in[z]]-=2;
        }
    }

    dfs2(1);
    for(int i=1; i<=n; i++){
        for(auto j: link[i]){
            if(dsu.find(i) != dsu.find(j)) deg[dsu.find(i)]++;
        }
    }
    for(int i=1; i<=n; i++) if(deg[i] == 1) leafCnt++;
    printf("%d\n", (leafCnt + 1) / 2);
}

컴파일 시 표준 에러 (stderr) 메시지

mergers.cpp: In function 'int main()':
mergers.cpp:67:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |     scanf("%d %d", &n, &k);
      |     ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:71:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |         scanf("%d %d", &x, &y);
      |         ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:75:34: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |     for(int i=1; i<=n; i++) scanf("%d", &arr[i]);
      |                             ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30