Create TwoSum.java

Author: harshithasudhakar

Math/TwoSum.java

@@ -0,0 +1,33 @@
+class TwoSum {
+    public int[] twoSumBrute(int[] nums, int target) { // brute-force O(n^2) time
+        int n = nums.length;
+        int[] result = new int[2];
+        for(int i = 0; i<n; i++){
+            for(int j = 0; j<n; j++){
+                if((nums[i]+nums[j]) == target && (i!=j)){
+                    result[0] = i;
+                    result[1] = j;
+                    return result;
+                }
+            }
+        }
+    }
+
+  public int[] twoSumHash(int[] nums, int target) { // 1-Hash approach O(n) time
+        Map<Integer, Integer> map = new HashMap<>();
+        int[] result = new int[2];
+
+        for(int i = 0; i<nums.length; i++){
+            int complement = target-nums[i];
+            if(map.containsKey(complement) && map.get(complement)!= i){
+                result[0] = i;
+                result[1] = map.get(complement);
+                return result;
+            }
+            map.put(nums[i], i);
+        }
+  }
+  
+  return result;
+}
+