support bazel complie this project and format code.

practical_exercises/10_day_practice/day5/virtual/seq.cpp

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+/* 虚基类调用次序(重要).cpp */
+//重要!!!
+#include <iostream>
+using namespace std;
+class A {
+  int a;
+
+public:
+  A() { cout << "Constructing A" << endl; }
+};
+class B {
+public:
+  B() { cout << "Constructing B" << endl; }
+};
+class B1 : virtual public B, virtual public A {
+public:
+  B1(int i) { cout << "Constructing B1" << endl; }
+};
+class B2 : public A, virtual public B {
+public:
+  B2(int j) { cout << "Constructing B2" << endl; }
+};
+class D : public B1, public B2 {
+public:
+  D(int m, int n) : B1(m), B2(n) { cout << "Constructing D" << endl; }
+  A a;
+};
+
+int main() {
+  D d(1, 2);
+  
+  return 0;
+}