Merge pull request Dijkstra-Edu#3 from VISHAL3003/vishal-patch-1

Commit #123 - Added TwoSum in cpp - 29-02-2023

Author: JRS296

Arrays & Strings/Two Sum/Two Sum 2.cpp

@@ -0,0 +1,68 @@
+//Brute Force
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        for(int i = 0;i<nums.size();i++) {
+            for(int j = i+1;j<nums.size();j++) {
+                if(nums[i] + nums[j] == target) return {i,j};
+            }
+        }
+        return {};
+    }
+};
+/*
+    Runtime: 2.2 ms
+    Memory Usage: 12.69 MB
+    Time Complexity : O(n^2)
+*/
+
+
+//One-Pass Hash Table
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        unordered_map<int, int> numMp;
+        int n = nums.size();
+
+        for(int i = 0; i < n; i++) {
+            int complement = target - nums[i];
+            if(numMp.count(complement)) {
+                return {numMp[complement], i};
+            }
+            numMp[nums[i]] = i;
+        }
+        return {};
+    }
+};
+/*
+    Runtime: 3 ms
+    Memory Usage: 14.12 MB
+    Time Complexity : O(n)
+*/
+
+
+//Two-pass Hash Table
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        unordered_map<int, int> numMp;
+        int n = nums.size();
+
+        for(int i = 0;i < n; i++) {
+            numMp[nums[i]] = i;
+        }
+
+        for(int i = 0; i < n; i++) {
+            int complement = target - nums[i];
+            if(numMp.count(complement) && numMp[complement] != i) {
+                return {i, numMp[complement]};
+            }
+        }
+        return {};
+    }
+};
+/*
+    Runtime: 11 ms
+    Memory Usage: 15.69 MB
+    Time Complexity : O(n)
+*/