Adding Maps

Author: Prashant Jain

src/in/knowledgegate/dsa/array/TwoSum.java

@@ -1,40 +1,37 @@
 package in.knowledgegate.dsa.array;
 
-import java.util.HashMap;
-import java.util.Map;
-
 /**
- * Given an array of integers nums and an integer target, return indices of the
- * two numbers such that they add up to target. You may assume that each input
- * would have exactly one solution, and you may not use the same element twice.
- * You can return the answer in any order.
+ * Given an array of integers nums and an integer
+ * target, return indices of the two numbers such
+ * that they add up to target. You may assume that
+ * each input would have exactly one solution, and
+ * you may not use the same element twice. You can
+ * return the answer in any order.
  * <p>
- * Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation:
- * Because nums[0] + nums[1] == 9, we return [0, 1].
+ * Example 1: Input: nums = [2,7,11,15], target =
+ * 9 Output: [0,1] Explanation: Because nums[0] +
+ * nums[1] == 9, we return [0, 1].
  * <p>
- * Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2]
+ * Example 2: Input: nums = [3,2,4], target = 6
+ * Output: [1,2]
  * <p>
- * Example 3: Input: nums = [3,3], target = 6 Output: [0,1]
+ * Example 3: Input: nums = [3,3], target = 6
+ * Output: [0,1]
  * <p>
  * <p>
- * Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <=
- * 109 Only one valid answer exists.
+ * Constraints: 2 <= nums.length <= 104 -109 <=
+ * nums[i] <= 109 -109 <= target <= 109 Only one
+ * valid answer exists.
  */
 public class TwoSum {
     public int[] twoSum(int[] nums, int target) {
-        Map<Integer, Integer> map = new HashMap<>();
         for (int i = 0; i < nums.length; i++) {
-            map.put(nums[i], i);
-        }
-
-        for (int i = 0; i < nums.length; i++) {
-            int num = target - nums[i];
-            int result = map.getOrDefault(num, -1);
-            if (result >= 0 && result != i) {
-                return new int[]{i, result};
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[i] + nums[j] == target) {
+                    return new int[] {i , j};
+                }
             }
         }
-
-        throw new IllegalArgumentException("invalid input");
+        throw new IllegalArgumentException("Invalid input");
     }
 }

src/in/knowledgegate/dsa/maps/TwoSum.java

@@ -0,0 +1,40 @@
+package in.knowledgegate.dsa.maps;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Given an array of integers nums and an integer target, return indices of the
+ * two numbers such that they add up to target. You may assume that each input
+ * would have exactly one solution, and you may not use the same element twice.
+ * You can return the answer in any order.
+ * <p>
+ * Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation:
+ * Because nums[0] + nums[1] == 9, we return [0, 1].
+ * <p>
+ * Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2]
+ * <p>
+ * Example 3: Input: nums = [3,3], target = 6 Output: [0,1]
+ * <p>
+ * <p>
+ * Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <=
+ * 109 Only one valid answer exists.
+ */
+public class TwoSum {
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> map = new HashMap<>();
+        for (int i = 0; i < nums.length; i++) {
+            map.put(nums[i], i);
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            int num = target - nums[i];
+            int result = map.getOrDefault(num, -1);
+            if (result >= 0 && result != i) {
+                return new int[]{i, result};
+            }
+        }
+
+        throw new IllegalArgumentException("invalid input");
+    }
+}