并查集

代码1：

#include <bits/stdc++.h>
using namespace std;

const int maxn = 1e5 + 10;
int par[maxn];
int rank[maxn];

void init(int n) {
    for(int i = 0; i < n; i ++) {
        par[i] = i;
        rank[i] = 0;
    }
}

int find(int x) {
    if(par[x] == x)
        return x;
    else
        return par[x] = find(par[x]);
}

int unite(int x, int y) {
    x = find(x);
    y = find(y);
    if(x == y) return;

    if(rank[x] < rank[y])
        par[x] = y;
    else {
        par[y] = x;
        if(rank[x] == rank[y])
            rank[x] ++;
    }
}

bool same(int x, int y) {
    return find(x) == find(y);
}

　　

代码2：

#include <bits/stdc++.h>
using namespace std;

int N;
int c;
int fa[20];

int dfs(int z) {
    if(fa[z] == z) return z;
    else
        return fa[z] = dfs(fa[z]);
}

int main() {
    scanf("%d", &N);
    for(int i = 1; i <= N; i ++)
        fa[i] = i;
    while(N --) {
        int x, y;
        scanf("%d", &c);
        scanf("%d%d", &x, &y);
        if(c == 0)
            fa[y] = dfs(x);
        else if(c == 1) {
            if(dfs(x) == dfs(y))
                printf("YES
");
            else
                printf("NO
");
        }
    }
    return 0;
}

代码3：

#include <bits/stdc++.h>
using namespace std;

const int maxn = 1e5 + 10;
int f[maxn];
int n;

int Find(int x) {
  if(x != f[x]) f[x] = Find(f[x]);
  return f[x];
}

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

int Merge(int x, int y) {
  int fx = Find(x);
  int fy = Find(y);
  if(fx != fy) {
    f[fx] = fy;
  }
}

int main() {

  return 0;
}