add: 220303 [cpp]

cpp/2203/220303.cpp

@@ -0,0 +1,40 @@
+#include <iostream>
+#include <vector>
+
+/**
+ * 413. Arithmetic Slices
+ * An integer array is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.
+ * For example, [1,3,5,7,9], [7,7,7,7], and [3,-1,-5,-9] are arithmetic sequences.
+ * Given an integer array nums, return the number of arithmetic subarrays of nums.
+ * A subarray is a contiguous subsequence of the array.
+ */
+
+class Solution {
+public:
+	static int numberOfArithmeticSlices(std::vector<int>& args) {
+		int n = args.size();
+		if (n < 3)
+			return 0;
+		args.push_back(0xFFFFFFF);
+		int prev = args[1], diff = args[1] - args[0], sliceBegin = 0, ret = 0;
+		for (int i = 2; i <= n; ++i) {
+			if (args[i] - prev != diff) {
+				// Last slice terminates at position i - 1
+				// Length i - sliceBegin
+				int len = i - sliceBegin - 2;
+				if (len > 0)
+					ret += (len * (1 + len)) >> 1;
+				diff = args[i] - prev;
+				sliceBegin = i - 1;
+			}
+			prev = args[i];
+		}
+		return ret;
+	}
+};
+
+int main() {
+	std::vector<int> args = {1,2,3,8,9,10};
+	std::cout << Solution::numberOfArithmeticSlices(args);
+	return 0;
+}

cpp/2203/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2203)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2203 220302.cpp)
+ADD_EXECUTABLE(2203 220303.cpp)