ptbhatcoder
diff --git a/‎leetCode/april/week1/single_number.js renamed to ‎leetCode/april/week1/1_single_number.js b/‎leetCode/april/week1/single_number.js renamed to ‎leetCode/april/week1/1_single_number.js
diff --git a/‎leetCode/april/week1/happy_number.js renamed to ‎leetCode/april/week1/2_happy_number.js b/‎leetCode/april/week1/happy_number.js renamed to ‎leetCode/april/week1/2_happy_number.js
diff --git a/‎leetCode/april/week1/maximum_subarray.js renamed to ‎leetCode/april/week1/3_maximum_subarray.js b/‎leetCode/april/week1/maximum_subarray.js renamed to ‎leetCode/april/week1/3_maximum_subarray.js
diff --git a/‎leetCode/april/week1/move_zeroes.js renamed to ‎leetCode/april/week1/4_move_zeroes.js b/‎leetCode/april/week1/move_zeroes.js renamed to ‎leetCode/april/week1/4_move_zeroes.js
diff --git a/‎leetCode/april/week1/best_time_to_buy_sell_stock_2.js renamed to ‎leetCode/april/week1/5_best_time_to_buy_sell_stock_2.js b/‎leetCode/april/week1/best_time_to_buy_sell_stock_2.js renamed to ‎leetCode/april/week1/5_best_time_to_buy_sell_stock_2.js
diff --git a/‎leetCode/april/week1/groupAnagrams.js renamed to ‎leetCode/april/week1/6_groupAnagrams.js b/‎leetCode/april/week1/groupAnagrams.js renamed to ‎leetCode/april/week1/6_groupAnagrams.js
diff --git a/‎leetCode/april/week1/7_couting_elements.js
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+/**
+ 
+Given an integer array arr, count element x such that x + 1 is also in arr.
+If there’re duplicates in arr, count them seperately.
+
+Example 1:
+Input: arr = [1,2,3]
+Output: 2
+Explanation: 1 and 2 are counted cause 2 and 3 are in arr.
+
+Example 2:
+Input: arr = [1,1,3,3,5,5,7,7]
+Output: 0
+Explanation: No numbers are counted, cause there's no 2, 4, 6, or 8 in arr.
+
+Example 3:
+Input: arr = [1,3,2,3,5,0]
+Output: 3
+Explanation: 0, 1 and 2 are counted cause 1, 2 and 3 are in arr.
+
+Example 4:
+Input: arr = [1,1,2,2]
+Output: 2
+Explanation: Two 1s are counted cause 2 is in arr.
+
+Constraints:
+1 <= arr.length <= 1000
+0 <= arr[i] <= 1000
+
+ */
+
+export const countElements = (nums) => {
+  const lookup = new Set(nums);
+  return nums.reduce(
+    (count, val) => (lookup.has(val + 1) ? count + 1 : count),
+    0
+  );
+};