add: 220406 [cpp]

cpp/2204/220406.cpp

@@ -0,0 +1,43 @@
+#include <vector>
+#include <iostream>
+
+class Solution {
+private:
+	static inline const int MAX_VALUE = 100 + 2;
+
+	static inline const int MOD = 1000000007;
+
+	inline static unsigned long long CX2(unsigned long long n) {
+		return (n & 1) ? ((n - 1 >> 1) * n) : ((n >> 1) * (n - 1));
+	}
+
+	inline static unsigned long long CX3(unsigned long long n) {
+		return (n - 2) * CX2(n) / 3;
+	}
+
+public:
+	static int threeSumMulti(const std::vector<int>& arr, const int target) {
+		unsigned long long cnt[3 * MAX_VALUE]{};
+		for (int i: arr)
+			++cnt[i];
+		unsigned long long ret = 0;
+
+		// 3 Different values
+		for (int i = 0; i < MAX_VALUE; ++i)
+			for (int j = i + 1; j < (target - i - j); ++j)
+				ret = (ret + (((cnt[target - i - j] * cnt[i]) % MOD) * cnt[j]) % MOD) % MOD;
+
+		// 2 Same Values
+		for (int i = 0; i < MAX_VALUE && target - i - i >= 0; ++i)
+			if (cnt[i] >= 2 && i + i + i != target)
+				ret = (ret + CX2(cnt[i]) * cnt[target - i - i] % MOD) % MOD;
+
+		// 3 Same values
+		return (ret + (3 * (target / 3) == target ? CX3(cnt[target / 3]) : 0)) % MOD;
+	}
+};
+
+int main() {
+	std::cout << Solution::threeSumMulti({0,0,0}, 0);
+	return 0;
+}

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220404-CN.cpp)
+ADD_EXECUTABLE(2204 220406.cpp)