support bazel complie this project and format code.

practical_exercises/10_day_practice/day7/unary_operator/BUILD

@@ -0,0 +1,13 @@
+# please run `bazel run //practical_exercises/10_day_practice/day7/unary_operator:time_increase`
+# please run `bazel run //practical_exercises/10_day_practice/day7/unary_operator:time_counter`
+
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+cc_binary(
+    name = "time_increase",
+    srcs = ["time_increase.cpp"],
+)
+cc_binary(
+    name = "time_counter",
+    srcs = ["time_counter.cpp"],
+)

practical_exercises/10_day_practice/day7/unary_operator/time_counter.cpp

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+/* 计数器前后自增.cpp */
+//设计一个计数器counter，用类成员重载自增运算符实现计数器的自增，用友元重载实现计数器的自减。
+#include <iostream>
+using namespace std;
+class Counter {
+private:
+  int n;
+
+public:
+  Counter(int i = 0) : n(i){};
+  Counter operator++();
+  Counter operator++(int);
+  friend Counter operator--(Counter &c);
+  friend Counter operator--(Counter &c, int);
+  void display();
+};
+Counter Counter::operator++() {
+  ++n;
+  return *this;
+}
+Counter Counter::operator++(int) {
+  Counter t = *this;
+  n++;
+  return t;
+}
+Counter operator--(Counter &c) {
+  --c.n;
+  return c;
+}
+Counter operator--(Counter& c, int) {
+    Counter t(c.n);
+    c.n--;
+    return t;
+}
+void Counter::display() { cout << "counter number=" << n << endl; }
+int main(int argc, char const *argv[]) {
+  Counter a;
+  ++a;
+  a.display();
+  a++;
+  a.display();
+  --a;
+  a.display();
+  a--;
+  a.display();
+  
+  return 0;
+}

practical_exercises/10_day_practice/day7/unary_operator/time_increase.cpp

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+/* 秒钟自增运算.cpp */
+//设计一个时间类Time，它能够完成秒钟的自增运算。
+
+#include <iostream>
+using namespace std;
+
+class Time {
+private:
+  int hour, minute, second;
+
+public:
+  Time(int h, int m, int s);
+  Time operator++();
+  //友元重载需要参数
+  friend Time operator--(Time &t);
+  void display();
+};
+
+Time::Time(int h, int m, int s) {
+  hour = h;
+  minute = m;
+  second = s;
+  if (hour >= 24)
+    hour = 0;
+  if (minute >= 60)
+    minute = 0;
+  if (second >= 60)
+    second = 0;
+}
+
+Time Time::operator++() {
+  ++second;
+  if (second >= 60) {
+    second = 0;
+    ++minute;
+    if (minute >= 60) {
+      minute = 0;
+      ++hour;
+      if (hour >= 24)
+        hour = 0;
+    }
+  }
+  return *this;
+}
+Time operator--(Time &t) {
+  --t.second;
+  if (t.second < 0) {
+    t.second = 59;
+    --t.minute;
+    if (t.minute < 0) {
+      t.minute = 59;
+      --t.hour;
+      if (t.hour < 0)
+        t.hour = 23;
+    }
+  }
+  return t;
+}
+void Time::display() { cout << hour << ":" << minute << ":" << second << endl; }
+int main(int argc, char const *argv[]) {
+  Time t1(23, 59, 59);
+  t1.display();
+  ++t1; //隐式调用
+  t1.display();
+  t1.operator++(); //显式调用
+  t1.display();
+  Time t2(24, 60, 60);
+  t2.display();
+  ++t2;
+  t2.display();
+  --t2;
+  t2.display();
+  
+  return 0;
+}