day56|冗余连接, 冗余连接II

最新推荐文章于 2025-12-31 21:25:26 发布

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#算法 #c++ #数据结构

冗余连接

108. 冗余连接 (kamacoder.com)

#include<vector>
#include<iostream>

using namespace std;
int n = 0;
vector<int> father = vector<int>(1001);
void init(){
    for(int i = 1; i < n + 1; i++){
        father[i] = i;
    }
}
int find(int i){  // 找根节点
    if(i == father[i]){
        return i;
    }
    return father[i] = find(father[i]); // 压缩作用，直接将i链接到根部
}
void join(int i, int j){
    i = find(i);
    j = find(j);
    if(i == j){
        return;
    }
    father[j] = i;
}
bool ifsame(int i, int j){
    i = find(i);
    j = find(j);
    return i == j;
}

int main(){
    cin >> n;
    init();
    for(int i = 0; i < n; i++){
        int u = 0, v = 0;
        cin >> u >> v;
        if(ifsame(u, v)){
            cout << u << " " << v << endl;
        }else{
            join(u, v);   
        }
    }
    return 0;
}

冗余连接II

109. 冗余连接II (kamacoder.com)

#include<iostream>
#include<vector>

using namespace std;

int n;

vector<int> father = vector<int>(1001);

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

int find(int i){
    if(i == father[i]){
        return i;
    }
    return father[i] = find(father[i]);
}

bool same(int i, int j){
    i = find(i);
    j = find(j);
    return i == j;
}

void join(int i, int j){
    i = father[i];
    j = father[j];
    if(i == j){
        return ;
    }
    father[j] = i;
}

bool valid(vector<vector<int>> &edges, int order){
    init();
    for(int i = 0; i < n; i++){
        if(i == order){
            continue;
        }
        if(same(edges[i][0], edges[i][1])){
            return false;
        }
        join(edges[i][0], edges[i][1]);
    }
}
void getRemoved(vector<vector<int>> &edges){
    init();
    for(int i = n - 1; i >= 0; i--){
        if(edges[i][0] == 0){
            continue;
        }
        if(same(edges[i][0], edges[i][1])){
            cout << edges[i][0] << " " << edges[i][1];
            return ;
        }
        join(edges[i][0], edges[i][1]);
    }
}
int main(){
    int s = 0, t = 0;
    cin >> n;
    vector<vector<int>> edges(n, vector<int>(2));
    vector<int> counts(n + 1);
    for(int i = n - 1; i >= 0; i--){
        cin >> s >> t;
        edges[i][0] = s;
        edges[i][1] = t;
        counts[t]++;
    }
    for(int i = 0; i < n; i++){
        if(counts[edges[i][1]] == 2){
            if(valid(edges, i)){
                cout << edges[i][0] << " " << edges[i][1];
                return 0;
            }
        }
    }
    getRemoved(edges);
    return 0;
}