[AcWing 238] 银河英雄传说

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点击查看代码

#include<bits/stdc++.h>

using namespace std;

typedef long long LL;

const int N = 3e4 + 10;

int p[N], sz[N], d[N];

int find(int x)
{
    if (p[x] != x) {
        int root = find(p[x]);
        d[x] += d[p[x]];
        p[x] = root;
    }
    return p[x];
}

void solve()
{
    int m;
    cin >> m;
    for (int i = 1; i <= N; i ++) {
        p[i] = i;
        sz[i] = 1;
    }
    while (m --) {
        char op;
        int a, b;
        cin >> op >> a >> b;
        int pa = find(a), pb = find(b);
        if (op == 'M') {
            if (pa != pb) {
                d[pa] = sz[pb];
                sz[pb] += sz[pa];
                p[pa] = pb;
            }
        }
        else {
            if (pa != pb)
                cout << "-1" << endl;
            else {
                cout << max(0, abs(d[b] - d[a]) - 1) << endl;
            }
        }
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    solve();

    return 0;
}

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1. 用带边权的并查集记录距离
   用 $d[i]$ 记录 $i$ 到根节点的距离，$sz[i]$ 记录以 $i$ 为根节点的点的个数