solve #1101: the earliest moment when everyone become friend in java

Author: anishLearnsToCode

Diff for: README.md

@@ -498,6 +498,7 @@
 | 1086 | 🔒 [High Five](https://leetcode.com/problems/high-five)                                                                                                                |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 1089 | [Duplicate Zeroes](https://leetcode.com/problems/duplicate-zeros)                                                                                                      |                                                                                       [![Java](assets/java.png)](src/DuplicateZeros.java)                                                                                        |                                                                                                                                   |
 | 1099 | 🔒 [Two Sum Less Than K](https://leetcode.com/problems/two-sum-less-than-k)                                                                                            |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 1101 | [The Earliest Moment When Everyone Become Friend](https://leetcode.com/problems/the-earliest-moment-when-everyone-become-friends)                                      |                                                                         [![Java](assets/java.png)](src/TheEarliestMomentWhenEveryoneBecomeFriends.java)                                                                          |                                                                                                                                   |
 | 1103 | [Distribute Candies to People](https://leetcode.com/problems/distribute-candies-to-people)                                                                             |                                                                                  [![Java](assets/java.png)](src/DistributeCandiesToPeople.java)                                                                                  |                                                                                                                                   |
 | 1108 | [Defanging an IP Address](https://leetcode.com/problems/defanging-an-ip-address)                                                                                       |                                                                                    [![Java](assets/java.png)](src/DefangingAnIPAddress.java)                                                                                     |                                                                                                                                   |
 | 1118 | 🔒 [Number of Days in a Month](https://leetcode.com/problems/number-of-days-in-a-month)                                                                                |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/TheEarliestMomentWhenEveryoneBecomeFriends.java

@@ -0,0 +1,63 @@
+// https://leetcode.com/problems/the-earliest-moment-when-everyone-become-friends
+// M = |logs|
+// T: O(N + M logM + M al(N)) al = inverse Ackermann function
+// S: O(N + logM)
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+public class TheEarliestMomentWhenEveryoneBecomeFriends {
+    private static final class DisjointSet {
+        private final int[] root, rank;
+
+        public DisjointSet(int size) {
+            root = new int[size];
+            rank = new int[size];
+            for (int i = 0 ; i < size ; i++) {
+                root[i] = i;
+                rank[i] = 1;
+            }
+        }
+
+        public int find(int num) {
+            if (num == root[num]) {
+                return num;
+            }
+            return root[num] = find(root[num]);
+        }
+
+        public boolean areConnected(int x, int y) {
+            return find(x) == find(y);
+        }
+
+        public void union(int x, int y) {
+            final int rootX = find(x), rootY = find(y);
+            if (rootX == rootY) {
+                return;
+            }
+            if (rank[rootX] > rank[rootY]) {
+                root[rootY] = rootX;
+            } else if (rank[rootX] < rank[rootY]) {
+                root[rootX] = rootY;
+            } else {
+                root[rootY] = rootX;
+                rank[rootX]++;
+            }
+        }
+    }
+
+    public int earliestAcq(int[][] logs, int n) {
+        final DisjointSet disjointSet = new DisjointSet(n);
+        Arrays.sort(logs, Comparator.comparingInt(a -> a[0]));
+        for (int[] log : logs) {
+            if (!disjointSet.areConnected(log[1], log[2])) {
+                disjointSet.union(log[1], log[2]);
+                n--;
+                if (n == 1) {
+                    return log[0];
+                }
+            }
+        }
+        return -1;
+    }
+}