add: 220530 [cpp]

cpp/2205/220530.cpp

@@ -0,0 +1,57 @@
+#include <algorithm>
+#include <random>
+#include <ctime>
+#include <cstdio>
+
+/**
+ * 29. Divide Two Integers
+ * Given two integers dividend and divisor, divide two integers without using multiplication, division, and mod operator.
+ * The integer division should truncate toward zero, which means losing its fractional part. For example, 8.345 would be truncated to 8, and -2.7335 would be truncated to -2.
+ * Return the quotient after dividing dividend by divisor.
+ * - Note: Assume we are dealing with an environment that could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For this problem, if the quotient is strictly greater than 231 - 1, then return 231 - 1, and if the quotient is strictly less than -231, then return -231.
+ */
+
+class Solution {
+public:
+	static int divide(int dividend, int divisor) {
+		unsigned ans = 0, cur = 1;
+		bool neg = (dividend ^ divisor) & 0x80000000;
+
+		unsigned r = 0x80000000 == divisor ? 0x80000000 : std::abs(divisor),
+				 d = 0x80000000 == dividend ? 0x80000000 : std::abs(dividend);
+
+		while (r < d) {
+			r <<= 1;
+			cur <<= 1;
+		}
+
+		while (cur) {
+			if (d >= r) {
+				ans += cur;
+				d -= r;
+			}
+			cur >>= 1;
+			r >>= 1;
+		}
+		if (neg)
+			return ans > 0x80000000 ? (-2147483647 - 1) : -ans;
+		return ans > 0x7FFFFFFF ? 2147483647 : ans;
+	}
+};
+
+int main() {
+	Solution::divide(-2147483647 - 1, -1);
+
+	std::mt19937 r(std::time(nullptr));
+
+	for (int N = 1048576; N--; ) {
+		int x = r(), y = r();
+		int d1 = x / y, d2 = Solution::divide(x, y);
+		if (d1 != d2) {
+			std::printf("Bad answer: (%d / %d) -> %d, but %d is expected.\n", x, y, d2, d1);
+			return -1;
+		}
+	}
+
+	return 0;
+}

cpp/2205/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2205)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2205 220529-CN.cpp)
+ADD_EXECUTABLE(2205 220530.cpp)

cpp/CMakeLists.txt

@@ -10,7 +10,7 @@ ELSE()
 ENDIF()
 
 IF(UNIX)
-    SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address -fno-omit-frame-pointer")
+    SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer")
 ENDIF()
 
 # Optimisation