add 3701

Author: fishercoder1534

paginated_contents/algorithms/4th_thousand/README.md

@@ -18,6 +18,7 @@
 | 3913 | [Sort Vowels by Frequency](https://leetcode.com/problems/sort-vowels-by-frequency/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3913.java) |                                                                               | Easy       |
 | 3908 | [Valid Digit Number](https://leetcode.com/problems/valid-digit-number/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3908.java) |                                                                               | Easy       |
 | 3978 | [Unique Middle Element](https://leetcode.com/problems/unique-middle-element/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3978.java) |                                                                               | Easy       |
+| 3701 | [Compute Alternating Sum](https://leetcode.com/problems/compute-alternating-sum/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3701.java) |                                                                               | Easy       |
 | 3502 | [Minimum Cost to Reach Every Position](https://leetcode.com/problems/minimum-cost-to-reach-every-position/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3502.java) |                                                                               | Easy       |
 | 3491 | [Phone Number Prefix](https://leetcode.com/problems/phone-number-prefix/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3491.java) |                                                                               | Easy       |
 | 3477 | [Fruits Into Baskets II](https://leetcode.com/problems/fruits-into-baskets-ii/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3477.java) |                                                                               | Easy       |

src/main/java/com/fishercoder/solutions/fourththousand/_3701.java

@@ -0,0 +1,17 @@
+package com.fishercoder.solutions.fourththousand;
+
+public class _3701 {
+    public static class Solution1 {
+        public int alternatingSum(int[] nums) {
+            int sum = 0;
+            for (int i = 0; i < nums.length; i++) {
+                if (i % 2 == 0) {
+                    sum += nums[i];
+                } else {
+                    sum -= nums[i];
+                }
+            }
+            return sum;
+        }
+    }
+}