Two-Hundred-Forty-Five Commit: Add Find the Middle Index in Array problem to Prefix Sum Section

Author: AAdewunmi

src/Prefix_Sum/Problem_1_Find_The_Middle_Index_In_Array.java

@@ -0,0 +1,22 @@
+package Prefix_Sum;
+
+// Problem Statement: Find the Middle Index in Array (easy)
+// LeetCode Question: 1991. Find the Middle Index in Array
+
+public class Problem_1_Find_The_Middle_Index_In_Array {
+    public int findMiddleIndex(int[] nums){
+        int totalSum = 0;
+        for (int num : nums) {
+            totalSum += num;
+        }
+        int leftSum = 0;
+        for (int i = 0; i < nums.length; i++) {
+            int rightSum = totalSum - leftSum - nums[i];
+            if (leftSum == rightSum) {
+                return i;
+            }
+            leftSum += nums[i];
+        }
+        return - 1;
+    }
+}