support bazel complie this project and format code.

practical_exercises/key_exercises/clock.cpp

@@ -0,0 +1,85 @@
+/* 时钟++运算符重载.cpp */
+#include <cmath>
+#include <iostream>
+using namespace std;
+
+/*
+ *  时钟类
+ */
+class Clock {
+private:
+  int Hour, Minute, Second;
+
+public:
+  Clock(int h = 0, int m = 0, int s = 0);
+  void ShowTime();
+  Clock &operator++();
+  Clock operator++(int);
+};
+
+/*
+ *  时钟类构造函数
+ */
+Clock::Clock(int h, int m, int s) {
+  if (h >= 0 && h < 24 && m >= 0 && m < 60 && s >= 0 && s < 60) {
+    Hour = h;
+    Minute = m;
+    Second = s;
+  } else
+    cout << "输入的时间格式错误!" << endl;
+}
+
+/*
+ *  显示时间
+ */
+void Clock::ShowTime() {
+  cout << Hour << ":" << Minute << ":" << Second << endl;
+}
+
+/*
+ *  时间递增一秒（重载前缀++运算符）
+ */
+Clock &Clock::operator++() {
+  Second++;
+  if (Second >= 60) {
+    Second = Second - 60;
+    Minute++;
+    if (Minute >= 60) {
+      Minute = Minute - 60;
+      Hour++;
+      Hour = Hour % 24;
+    }
+  }
+  return *this;
+}
+
+/*
+ *  时间递增一秒（重载后缀++运算符）
+ */
+Clock Clock::operator++(int) {
+  Clock old = *this;
+  ++(*this);
+  return old;
+}
+
+/*
+ *  主函数
+ */
+int main() {
+  Clock myClock(23, 59, 59);
+  cout << "初始化显示时间为:\t\t";
+  myClock.ShowTime();
+
+  cout << "执行myClock++后的时间为:\t";
+
+  //先执行ShowTime()，输出myClock=23:59:59，
+  //再执行myClock++，此时myClock=00:00:00
+  (myClock++).ShowTime();
+
+  cout << "执行++myClock后的时间为:\t";
+
+  //先执行++myClock，此时myClock=00:00:01
+  //再执行ShowTime()，输出myClock=00:00:01
+  (++myClock).ShowTime();
+  
+}