support bazel complie this project and format code.

practical_exercises/10_day_practice/day6/abstract_class/BUILD

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+# please run `bazel run //practical_exercises/10_day_practice/day6/abstract_class:main`
+
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "main",
+    srcs = ["main.cpp"],
+)

practical_exercises/10_day_practice/day6/abstract_class/main.cpp

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+/* 抽象类.cpp */
+#include <iostream>
+using namespace std;
+class Figure {
+protected:
+  double x, y;
+
+public:
+  void set(double i, double j) {
+    x = i;
+    y = j;
+  }
+  virtual void area() = 0;
+};
+
+class Trianle : public Figure {
+public:
+  void area() { cout << "三角形面积：" << x * y * 0.5 << endl; }
+};
+class Rectangle : public Figure {
+public:
+  void area() { cout << "这是矩形，它的面积是：" << x * y << endl; }
+};
+
+int main(int argc, char const *argv[]) {
+  //定义抽象类指针
+  Figure *pF = NULL;
+  // Figure f1; 抽象类不能被实例化
+  Rectangle r;
+  Trianle t;
+  t.set(10, 20);
+  pF = &t;
+  pF->area();
+  r.set(10, 20);
+  pF = &r;
+  pF->area();
+  //定义抽象类引用
+  Figure &rF = t;
+  rF.set(20, 20);
+  rF.area();
+  
+  return 0;
+}