premium leetcode

Author: ayoubzulfiqar

README.md

@@ -62,6 +62,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [Excel Sheet Column Title](ExcelSheetColumnTitle/excel_sheet_column_title.dart)
 - [Majority Element](MajorityElement/majority_element.dart)
 - [The Skyline Problem](TheSkylineProblem/the_skyline_problem.dart)
+- [Two Sum III - Data Structure Design](TwoSum-III-DataStructureDesign/two_sum_III_data_structure_design.dart)
 
 ## Reach me via
 

TwoSum-III-DataStructureDesign/two_sum_III_data_structure_design.dart

@@ -0,0 +1,62 @@
+/*
+
+ -* Two Sum III - Data Structure Design *-
+
+
+Design and implement a TwoSum class. It should support the following operations:addandfind.
+add- Add the number to an internal data structure.
+find- Find if there exists any pair of numbers which sum is equal to the value.
+Example 1:
+add(1); add(3); add(5);
+find(4) -> true
+find(7) -> false
+Example 2:
+add(3); add(1); add(2);
+find(3) -> true
+find(6) -> false
+
+
+
+*/
+
+import 'dart:collection';
+
+class A {
+/*
+
+Approach 1:
+using two hash-set to store unique number and unique sum when add(), add to unique sum and num,
+this will have O(n) time for add(), and O(1) for find().
+The space complexity though is O(n^2), which unique set for sum will consume O(n^2) space
+
+*/
+
+  HashMap<int, int> elements = HashMap<int, int>();
+
+  void add(int number) {
+    if (elements.containsKey(number)) {
+      elements.forEach((key, value) {
+        key = number;
+        value = elements.values.elementAt(number) + 1;
+      });
+    } else {
+      elements.forEach((key, value) {
+        key = number;
+        value = 1;
+      });
+    }
+  }
+
+  bool find(int value) {
+    for (int i in elements.keys) {
+      int target = value - i;
+      if (elements.containsKey(target)) {
+        if (i == target && elements.values.elementAt(target) < 2) {
+          continue;
+        }
+        return true;
+      }
+    }
+    return false;
+  }
+}

TwoSum-III-DataStructureDesign/two_sum_III_data_structure_design.go

@@ -0,0 +1 @@
+package main