update

practical_exercises/10_day_practice/day1/打印练习.cpp

@@ -0,0 +1,24 @@
+#include<iostream>
+using namespace std;
+int main(int argc, char const *argv[])
+{
+    int i,j,k,f;
+    for (i=1;i<=4;i++){
+        for (j=1;j<=30;j++)
+            cout<<" ";
+        for (k=1;k<=8-2*i;k++)
+            cout<<" ";
+        for (f=1;f<=2*i;f++)
+            cout<<'*';
+        cout<<endl;
+    }
+    for(i=1;i<=3;i++){
+        for (j=1;j<=30;j++)
+            cout<<" ";
+        for (f=1;f<=7-2*i;f++)
+            cout<<'*';
+        cout<<endl;
+    }
+    system("pause");
+    return 0;
+}

practical_exercises/10_day_practice/day1/是否闰年‘.cpp

@@ -0,0 +1,20 @@
+#include<iostream>
+using namespace std;
+int main(int argc, char const *argv[])
+{
+    int year;
+    bool isLeapYear;
+    cout<<"Enter the year: ";
+    cin>>year;
+    isLeapYear = (((year%4==0)&&(year%100!=0))||(year%400==0));
+    if(isLeapYear)
+    {
+        cout<<year<<" is a leap year"<<endl;
+    }
+    else
+    {
+        cout<<year<<" is not a leap year"<<endl;
+    }
+    system("pause");
+    return 0;
+}

practical_exercises/10_day_practice/day1/注释.cpp

@@ -0,0 +1,16 @@
+#include<iostream>
+
+
+一种条件编译指令注释
+
+
+//另一种注释方法
+#if 0
+asd
+#endif
+
+//打开注释
+//条件编译指令
+#if 1
+asData
+#endif

practical_exercises/10_day_practice/day1/联合体学习.cpp

@@ -0,0 +1,18 @@
+#include<iostream>
+using namespace std;
+//相同的内存地址
+union myun 
+{
+    struct { int x; int y; int z; }u; 
+    int k; 
+}a; 
+int main() 
+{ 
+    a.u.x =4;
+    a.u.y =5; 
+    a.u.z =6; 
+    a.k = 0; //覆盖掉第一个int空间值
+    printf("%d %d %d %d\n",a.u.x,a.u.y,a.u.z,a.k);
+    system("pause");
+    return 0;
+}