PAT1118. Birds in Forest （并查集）

思路：并查集一套带走。

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AC代码

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int maxn = 10000+5;int par[maxn], vis[maxn];int findRoot(int x) {    return x == par[x] ? x : par[x] = findRoot(par[x]);}void unionSet(int x, int y) {    x = findRoot(x);    y = findRoot(y);    if(x != y) {        par[x] = y;    }}void init(int n) {    memset(vis, 0, sizeof(vis));    for(int i = 0; i <= n; i++) {        par[i] = i;    }}int main() {    int n, k, q, len;    len = -1;    scanf("%d", &n);    init(maxn);    for(int i = 0; i < n; i++) {        int x, y;        scanf("%d%d", &k, &x);        len = max(len, x);        for(int j = 1; j < k; j++) {            scanf("%d", &y);            len = max(len, y);            unionSet(x, y);            x = y;        }    }    int tol = 0;    for(int i = 1; i <= len; i++) {        int root = findRoot(i);        if(!vis[root]) {            vis[root] = 1;            tol++;        }    }    printf("%d %d\n", tol, len);    scanf("%d", &q);    int x, y;    for(int i = 0; i < q; i++) {        scanf("%d%d", &x, &y);        x = findRoot(x);        y = findRoot(y);        if(x == y) {            printf("Yes\n");        } else {            printf("No\n");        }    }    return 0;}

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