support bazel complie this project and format code.

practical_exercises/10_day_practice/day7/equal_operator/BUILD

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+# please run `bazel run //practical_exercises/10_day_practice/day7/equal_operator:equal_operator`
+
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "equal_operator",
+    srcs = ["equal_operator.cpp"],
+)

practical_exercises/10_day_practice/day7/equal_operator/equal_operator.cpp

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+/* =运算符重载.cpp */
+//例题ch.cppi
+#include <iostream>
+using namespace std;
+class X {
+public:
+  X &operator=(const X &x) {
+    cout << "a:";
+    return *this;
+  };
+};
+int main() {
+  X obj1, obj2, obj3;
+  obj1 = obj2;          //调用重载“=”
+  obj1.operator=(obj2); //调用重载“=”
+  obj1 = obj2 = obj3;   //调用重载“=”
+  
+}