Add files via upload

Author: 17tanya

Hash Table/Two_Sum.java

@@ -0,0 +1,29 @@
+//LeetCode 1. Two Sum
+//Question Link - https://leetcode.com/problems/two-sum/
+
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        int result[] = new int[2];
+        
+        //to store the numbers which have already been encountered
+        //key = number in array, value = index of the number
+        Map<Integer, Integer> seen = new HashMap<>();
+        
+        for(int i = 0 ; i < nums.length ; i++){
+            //the number nums[i] is alreday in the array
+            //check if (target - nums[i]) is also in the array or not 
+            int complement = target - nums[i];
+            
+            //we check if we have already encountered complement or not.
+            if(seen.containsKey(complement)){
+                return new int[]{seen.get(complement), i};
+            }
+            
+            //if complement does not exsist, we must store the current number in seen
+            //The current number could be the complement of some number to be visited further in the array
+            seen.put(nums[i], i);
+        }
+        
+        return result;
+    }
+}