【2018夏令营】【普及】第一天基本数据结构

1、并查集的模板 （有路径压缩， 没有合并的优化）

 P3367 【模板】并查集

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>

using namespace std;

int fa[10005];

void init(int n) {
    memset(fa, 0, sizeof(fa));
    for (int i = 1; i <= n; ++i) {
        fa[i] = i;
    }
}

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

void unionSet (int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) {
        return ;
    }
    fa[x] = y;
}

int main() {
    int n, m;
    cin >> n >> m;
    init(n);
    for (int i = 0; i < m; ++i) {
        int opt, x, y;
        cin >> opt >> x >>y;
        if (opt == 1) {
            unionSet(x, y);
        } else if (opt == 2) {
            char ans = find(x) == find(y) ? 'Y' : 'N';
            cout << ans << endl;
        } else {

        }
    }
    return 0;
}

P1551 亲戚

https://www.luogu.org/problemnew/show/P1551

给定一堆人，给出亲戚关系，然后q个询问，问任意两个人是否是亲戚关系 （还是裸的并查集）

#include <iostream>
#include <cstdio>
//#include <>
using namespace std;

int fa[6000];

void initUnionSet(int n) {
    for(int i = 0; i <= n; ++i) {
        fa[i] = i;
    }
}

//查询做了路径压缩
int find(int x) {
    return x == fa[x] ? x : fa[x] = find(fa[x]);
}

//合并没有做优化，暴力合并
void unionSet(int x, int y) {
    int xx = find(x);
    int yy = find(y);
    if (xx == yy) { return; }
    fa[xx] = yy;
}

int main() {
    int n, m, p;
    scanf("%d %d %d", &n, &m, &p);
    initUnionSet(n);
    for (int i = 0; i < m; ++i) {
        int x, y;
        scanf("%d %d", &x, &y);
        unionSet(x, y);
    }
    for (int i = 0; i < p ; ++i) {
        int x, y;
        scanf("%d %d", &x, &y);
        string answer = find(x) == find(y) ? "Yes" : "No";
        printf("%s
", answer.c_str());
    }
    return 0;
}