solves #170: Two Sum III: Data structure design

Author: anishLearnsToCode

README.md

@@ -163,7 +163,7 @@
 | 167  | [Two Sum II - Input Array is Sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted)                                                                   |                                                       [![Java](assets/java.png)](src/TwoSumIIInputArrayIsSorted.java) [![Python](assets/python.png)](python/two_sum_ii.py)                                                       |                                                                                                                                   |
 | 168  | [Excel Sheet Column Title](https://leetcode.com/problems/excel-sheet-column-title)                                                                                     |                                                  [![Java](assets/java.png)](src/ExcelSheetColumnTitle.java) [![Python](assets/python.png)](python/excel_sheet_column_title.py)                                                   |                                                                                                                                   |
 | 169  | [Majority Element](https://leetcode.com/problems/majority-element)                                                                                                     |                                                         [![Java](assets/java.png)](src/MajorityElement.java) [![Python](assets/python.png)](python/majority_element.py)                                                          |                                                                                                                                   |
-| 170  | 🔒 [Two Sum  III - Data Structure Design](https://leetcode.com/problems/two-sum-iii-data-structure-design)                                                             |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 170  | 🔒 [Two Sum  III - Data Structure Design](https://leetcode.com/problems/two-sum-iii-data-structure-design)                                                             |                                                                                [![Java](assets/java.png)](src/TwoSumIIIDataStructureDesign.java)                                                                                 |                                                                                                                                   |
 | 171  | [Excel Sheet Column Number](https://leetcode.com/problems/excel-sheet-column-number)                                                                                   |                                                 [![Java](assets/java.png)](src/ExcelSheetColumnNumber.java) [![Python](assets/python.png)](python/excel_sheet_column_number.py)                                                  |                                                                                                                                   |
 | 172  | [Factoring Trailing Zeroes](https://leetcode.com/problems/factorial-trailing-zeroes)                                                                                   |                                                 [![Java](assets/java.png)](src/FactorialTrailingZeros.java) [![Python](assets/python.png)](python/factorial_trailing_zeroes.py)                                                  |                                                                                                                                   |
 | 173  | [Binary Search Tree Iterator](https://leetcode.com/problems/binary-search-tree-iterator)                                                                               |                                                                                  [![Java](assets/java.png)](src/BinarySearchTreeIterator.java)                                                                                   |                                                                                                                                   |

src/TwoSumIIIDataStructureDesign.java

@@ -0,0 +1,34 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class TwoSumIIIDataStructureDesign {
+    static class TwoSum {
+        private final Map<Integer, Integer> map = new HashMap<>();
+
+        // T: O(1)
+        public void add(int number) {
+            map.put(number, map.getOrDefault(number, 0) + 1);
+        }
+
+        // N: number of unique elements we have seen so far
+        // T: O(N)
+        public boolean find(int sum) {
+            for (int current : map.keySet()) {
+                final int required = sum - current;
+                if (required == current) {
+                    if (map.get(required) >= 2) {
+                        return true;
+                    } else {
+                        continue;
+                    }
+                }
+
+                if (map.containsKey(required)) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}