oj.uz

Submission #25730

# Submission time Handle Problem Language Result Execution time Memory
25730 2017-06-23T19:25:22 Z gs14004 Pipes (CEOI15_pipes) C++11
100 / 100
 490 ms 14984 KB 
#include <cstdio>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
typedef pair<int,int> pi;
  
struct disj{
    int pa[100005];
    void init(int n){
        for(int i=0; i<=n; i++) pa[i] = i;
    }
    int find(int x){
        return pa[x] = (pa[x] == x ? x : find(pa[x]));
    }
    bool uni(int p, int q){
        p = find(p);
        q = find(q);
        if(p == q) return 0;
        pa[q] = p;
        find(q);
        return 1;
    }
}disj1, disj2;
  
int n, m;
vector<pi> bri;
vector<int> graph[100005];
  
int par[100005][17], dep[100005];
bool vis[100005];
  
void dfs(int x, int pa){
    vis[x] = 1;
    par[x][0] = pa;
    for (auto &i : graph[x]){
        if(i == pa) continue;
        dep[i] = dep[x] + 1;
        dfs(i,x);
    }
}
  
int lca(int x, int y){
    if(dep[x] < dep[y]) swap(x,y);
    int dx = dep[x] - dep[y];
    for(int i=0; i<17; i++){
        if((dx >> i) & 1) x = par[x][i];
    }
    for(int i=16; i>=0; i--){
        if(par[x][i] != par[y][i]){
            x = par[x][i];
            y = par[y][i];
        }
    }
    if(x != y) x = par[x][0];
    return x;
}
  
int up[100005];
  
void dfs2(int x, int pa){
    vis[x] = 1;
    for (auto &i : graph[x]){
        if(i == pa) continue;
        dfs2(i,x);
        up[x] = max(up[x], up[i] - 1);
    }
    if(pa != 0 && up[x] == 0) printf("%d %d\n",pa,x);
}

int main(){
    scanf("%d %d\n",&n,&m);
    disj1.init(n);
    disj2.init(n);
    while(m--){
        int u = 0, v = 0;
        char str[15];
        fgets(str,15,stdin);
        int pos = 0;
        while(str[pos] != ' '){
            u = (10 * u) + (str[pos] - '0');
            pos++;
        }
        pos++;
        while(str[pos] != '\n' && str[pos]){
            v = (10 * v) + (str[pos] - '0');
            pos++;
        }
        if(disj1.uni(u,v)){
            graph[u].push_back(v);
            graph[v].push_back(u);
        }
        else if(disj2.uni(u,v)){
            bri.push_back(pi(u,v));
        }
    }
    for(int i=1; i<=n; i++){
        if(!vis[i]){
            dfs(i,0);
        }
    }
    memset(vis, 0, sizeof(vis));
    for(int i=1; i<17; i++){
        for(int j=1; j<=n; j++){
            par[j][i] = par[par[j][i-1]][i-1];
        }
    }
    for(auto &i : bri){
        int l = lca(i.first,i.second);
        up[i.first] = max(up[i.first],dep[i.first] - dep[l]);
        up[i.second] = max(up[i.second],dep[i.second] - dep[l]);
    }
    for(int i=1; i<=n; i++){
        if(!vis[i]) dfs2(i, 0);     
    }
}

Compilation message

pipes.cpp: In function 'int main()':
pipes.cpp:72:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d\n",&n,&m);
     ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:78:14: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         fgets(str,15,stdin);
         ~~~~~^~~~~~~~~~~~~~

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 2816 KB Output is correct
2 Correct 3 ms 2816 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 3328 KB Output is correct
2 Correct 6 ms 3328 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 34 ms 3148 KB Output is correct
2 Correct 33 ms 3136 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 54 ms 4020 KB Output is correct
2 Correct 61 ms 3992 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 108 ms 5628 KB Output is correct
2 Correct 106 ms 6220 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 202 ms 11240 KB Output is correct
2 Correct 175 ms 11248 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 276 ms 12532 KB Output is correct
2 Correct 261 ms 12272 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 367 ms 14812 KB Output is correct
2 Correct 350 ms 14984 KB Output is correct

Subtask #9
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 424 ms 14776 KB Output is correct
2 Correct 401 ms 14852 KB Output is correct

Subtask #10
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 490 ms 14204 KB Output is correct
2 Correct 478 ms 14496 KB Output is correct