solves #3184: Count Pairs That Form a Complete Day I in java

Author: anishLearnsToCode

Diff for: README.md

@@ -918,7 +918,7 @@
 | 3173 | 🔒 [Bitwise OR of Adjacent Elements](https://leetcode.com/problems/bitwise-or-of-adjacent-elements)                                                                    |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3174 | [Clear Digits](https://leetcode.com/problems/clear-digits)                                                                                                             |                                                                                         [![Java](assets/java.png)](src/ClearDigits.java)                                                                                         |                                                                                                                                   |
 | 3178 | [Find the Child Who Has the Ball After K Seconds](https://leetcode.com/problems/find-the-child-who-has-the-ball-after-k-seconds)                                       |                                                                           [![Java](assets/java.png)](src/FindTheChildWhoHasTheBallAfterKSeconds.java)                                                                            |                                                                                                                                   |
-| 3184 | [Count Pairs That Form a Complete Day I](https://leetcode.com/problems/count-pairs-that-form-a-complete-day-i)                                                         |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 3184 | [Count Pairs That Form a Complete Day I](https://leetcode.com/problems/count-pairs-that-form-a-complete-day-i)                                                         |                                                                               [![Java](assets/java.png)](src/CountPairsThatFormACompleteDayI.java)                                                                               |                                                                                                                                   |
 | 3190 | [Find Minimum Operations to Make All Elements Divisible by Three](https://leetcode.com/problems/find-minimum-operations-to-make-all-elements-divisible-by-three)       |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3194 | [Minimum Average of Smallest and Largest Elements](https://leetcode.com/problems/minimum-average-of-smallest-and-largest-elements)                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3199 | [Count Triplets With Even XOR Set Bits I](https://leetcode.com/problems/count-triplets-with-even-xor-set-bits-i)                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/CountPairsThatFormACompleteDayI.java

@@ -0,0 +1,22 @@
+// https://leetcode.com/problems/count-pairs-that-form-a-complete-day-i
+// T: O(N)
+// S: O(N)
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class CountPairsThatFormACompleteDayI {
+    public int countCompleteDayPairs(int[] hours) {
+        final Map<Integer, Integer> frequencies = new HashMap<>();
+        int pairs = 0;
+
+        for (int element : hours) {
+            int required = (24 - (element % 24)) % 24;
+            int current = element % 24;
+            pairs += frequencies.getOrDefault(required, 0);
+            frequencies.put(current, frequencies.getOrDefault(current, 0) + 1);
+        }
+
+        return pairs;
+    }
+}