solves check array formation through concatenation

Author: anishLearnsToCode

Diff for: README.md

@@ -406,7 +406,7 @@
 | 1624 | [Largest Substring Between Two Equal Characters](https://leetcode.com/problems/largest-substring-between-two-equal-characters)                            |                                                    [![Java](assets/java.png)](src/LargestSubStringBetweenTwoEqualCharacters.java)                                                    |                                                                                                                                   |
 | 1629 | [Slowest Key](https://leetcode.com/problems/slowest-key)                                                                                                  |                                                                   [![Java](assets/java.png)](src/SlowestKey.java)                                                                    |                                                                                                                                   |
 | 1636 | [Sort Array by Increasing Frequency](https://leetcode.com/problems/sort-array-by-increasing-frequency)                                                    |                                                         [![Java](assets/java.png)](src/SortArrayByIncreasingFrequency.java)                                                          |                                                                                                                                   |
-| 1640 | [Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation)                                  |                                                                                                                                                                                      |                                                                                                                                   |
+| 1640 | [Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation)                                  |                                                     [![Java](assets/java.png)](src/CheckArrayFormationThroughConcatenation.java)                                                     |                                                                                                                                   |
 | 1646 | [Get Maximum in Generated Array](https://leetcode.com/problems/get-maximum-in-generated-array)                                                            |                                                                                                                                                                                      |                                                                                                                                   |
 | 1652 | [Defuse the Bomb](https://leetcode.com/problems/defuse-the-bomb)                                                                                          |                                                                                                                                                                                      |                                                                                                                                   |
 | 1656 | [Design an Ordered Stream](https://leetcode.com/problems/design-an-ordered-stream)                                                                        |                                                                                                                                                                                      |                                                                                                                                   |

Diff for: src/CheckArrayFormationThroughConcatenation.java

@@ -0,0 +1,24 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class CheckArrayFormationThroughConcatenation {
+    public boolean canFormArray(int[] arr, int[][] pieces) {
+        final Map<Integer, Integer> positions = getPositions(arr);
+        for (int[] piece : pieces) {
+            if (!positions.containsKey(piece[0])) return false;
+            if (positions.get(piece[0]) + piece.length > arr.length) return false;
+            for (int i = 0, j = positions.get(piece[0]); i < piece.length ; i++, j++) {
+                if (piece[i] != arr[j]) return false;
+            }
+        }
+        return true;
+    }
+
+    private Map<Integer, Integer> getPositions(int[] array) {
+        final Map<Integer, Integer> positions = new HashMap<>();
+        for (int index = 0 ; index < array.length ; index++) {
+            positions.put(array[index], index);
+        }
+        return positions;
+    }
+}