Create ant-on-the-boundary.cpp

Author: kamyu104

C++/ant-on-the-boundary.cpp

@@ -0,0 +1,17 @@
+// Time:  O(n)
+// Space: O(1)
+
+// prefix sum
+class Solution {
+public:
+    int returnToBoundaryCount(vector<int>& nums) {
+        int result = 0, curr = 0;
+        for (const auto& x : nums) {
+            curr += x;
+            if (curr == 0) {
+                ++result;
+            }
+        }
+        return result;
+    }
+};