add 2678

Author: fishercoder1534

Diff for: paginated_contents/algorithms/3rd_thousand/README.md

@@ -18,6 +18,7 @@
 | 2697 | [Lexicographically Smallest Palindrome](https://leetcode.com/problems/lexicographically-smallest-palindrome/)                                                            | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2697.java)                                       |                                      | Easy                           |
 | 2696 | [Minimum String Length After Removing Substrings](https://leetcode.com/problems/minimum-string-length-after-removing-substrings/)                                                            | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2696.java)                                       |                                      | Easy                           |
 | 2673 | [Make Costs of Paths Equal in a Binary Tree](https://leetcode.com/problems/make-costs-of-paths-equal-in-a-binary-tree/)                                                                                      | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2673.java)                                       |                                      | Medium                         |Tree, DFS, Greedy
+| 2678 | [Number of Senior Citizens](https://leetcode.com/problems/number-of-senior-citizens/)                                                                                      | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2678.java)                                       |                                      | Easy                           |
 | 2670 | [Find the Distinct Difference Array](https://leetcode.com/problems/find-the-distinct-difference-array/)                                                                                      | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2670.java)                                       |                                      | Easy                           |
 | 2643 | [Row With Maximum Ones](https://leetcode.com/problems/row-with-maximum-ones/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2643.java)                                       |                                      | Easy                           |
 | 2641 | [Cousins in Binary Tree II](https://leetcode.com/problems/cousins-in-binary-tree-ii/)                                                                                       | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2641.java)                                       |                                      | Medium                         |Tree, BFS, HashTable

Diff for: src/main/java/com/fishercoder/solutions/thirdthousand/_2678.java

@@ -0,0 +1,15 @@
+package com.fishercoder.solutions.thirdthousand;
+
+public class _2678 {
+    public static class Solution1 {
+        public int countSeniors(String[] details) {
+            int seniors = 0;
+            for (String detail : details) {
+                if (Integer.parseInt(detail.substring(11, 13)) > 60) {
+                    seniors++;
+                }
+            }
+            return seniors;
+        }
+    }
+}