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package class_2021_12_2_week;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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// 链接测试 : https://leetcode.com/problems/find-all-people-with-secret/
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public class Code01_FindAllPeopleWithSecret {
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public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {
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// 0~n-1号专家，各自建立小集合
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// (0, firstPerson)合在一起，作为知道秘密的集合
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UnionFind uf = new UnionFind(n, firstPerson);
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int m = meetings.length;
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Arrays.sort(meetings, (a, b) -> a[2] - b[2]);
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// [1,7,1] [2,4,2] [3,6,2]
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// 1,7 2,4 3,6
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int[] help = new int[m << 1];
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help[0] = meetings[0][0];
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help[1] = meetings[0][1];
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int size = 2;
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for (int i = 1; i < m; i++) {
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// i 2
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if (meetings[i][2] != meetings[i - 1][2]) {
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share(help, size, uf);
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help[0] = meetings[i][0];
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help[1] = meetings[i][1];
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size = 2;
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} else {
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help[size++] = meetings[i][0];
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help[size++] = meetings[i][1];
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}
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}
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share(help, size, uf);
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List<Integer> ans = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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if (uf.know(i)) {
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ans.add(i);
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}
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}
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return ans;
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}
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public static void share(int[] help, int size, UnionFind uf) {
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for (int i = 0; i < size; i += 2) {
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uf.union(help[i], help[i + 1]);
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}
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for (int i = 0; i < size; i++) {
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if (!uf.know(help[i])) {
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uf.isolate(help[i]);
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}
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}
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}
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public static class UnionFind {
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public int[] father;
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public boolean[] sect;
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public int[] help;
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public UnionFind(int n, int first) {
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father = new int[n];
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sect = new boolean[n];
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help = new int[n];
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for (int i = 1; i < n; i++) {
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father[i] = i;
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}
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father[first] = 0;
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sect[0] = true;
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}
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private int find(int i) {
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int hi = 0;
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while (i != father[i]) {
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help[hi++] = i;
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i = father[i];
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}
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for (hi--; hi >= 0; hi--) {
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father[help[hi]] = i;
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}
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return i;
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}
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public void union(int i, int j) {
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int fatheri = find(i);
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int fatherj = find(j);
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if (fatheri != fatherj) {
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father[fatherj] = fatheri;
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sect[fatheri] |= sect[fatherj];
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}
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}
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public boolean know(int i) {
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return sect[find(i)];
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}
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public void isolate(int i) {
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father[i] = i;
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}
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}
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}
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