FriendCircles
FriendCircles.java 源码
package datastructure.disjointset.leetcode;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
/**
* @author roseduan
* 朋友圈
*/
public class FriendCircles {
/**
* 深度优先搜索的思路
*/
public int findCircleNum1(int[][] M) {
boolean[] visited = new boolean[M.length];
int res = 0;
for (int i = 0; i < M.length; i++) {
if (!visited[i]) {
dfs(M, i, visited);
res++;
}
}
return res;
}
private void dfs(int[][] m, int i, boolean[] visited) {
for (int j = 0; j < m.length; j++) {
if (m[i][j] == 1 && !visited[j]) {
visited[j] = true;
dfs(m, j, visited);
}
}
}
/**
* 广度优先的思路
*/
public int findCircleNum2(int[][] M) {
boolean[] visited = new boolean[M.length];
int res = 0;
Queue<Integer> queue = new LinkedList<>();
for (int i = 0; i < M.length; i++) {
if (!visited[i]) {
queue.add(i);
while (!queue.isEmpty()) {
int s = queue.poll();
visited[s] = true;
for (int j = 0; j < M.length; j++) {
if (M[s][j] == 1 && !visited[j]) {
queue.add(j);
}
}
}
res++;
}
}
return res;
}
/**
* 使用并查集解决
*/
public int findCircleNum3(int[][] M) {
int[] parent = new int[M.length];
Arrays.fill(parent, -1);
for (int i = 0; i < M.length; i++) {
for (int j = 0; j < M[i].length; j++) {
if (M[i][j] == 1 && i != j) {
union(parent, i, j);
}
}
}
int res = 0;
for (int p : parent) {
if (p != -1) {
res++;
}
}
return res;
}
private int find(int[] parent, int i) {
if (parent[i] == -1) {
return i;
}
return find(parent, parent[i]);
}
private void union(int[] parent, int x, int y) {
int xset = find(parent, x);
int yset = find(parent, y);
if (xset != yset) {
parent[xset] = yset;
}
}
}
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