Create count-alternating-subarrays.cpp

Author: kamyu104

C++/count-alternating-subarrays.cpp

@@ -0,0 +1,17 @@
+// Time:  O(n)
+// Space: O(1)
+
+// dp
+class Solution {
+public:
+    long long countAlternatingSubarrays(vector<int>& nums) {
+        int64_t result = 0;
+        for (int i = 0, curr = 0; i < size(nums); ++i) {
+            if (i - 1 >= 0 && nums[i - 1] == nums[i]) {
+                curr = 0;
+            }
+            result += ++curr;
+        }
+        return result;
+    }
+};