Synchronization of old projects

Part1

C#基础/Lesson7_函数练习/Program.cs

@@ -0,0 +1,85 @@
+using System;
+namespace Lesson7
+{
+    class Program
+    {
+        static int Compare(int a, int b)
+        {
+            int max = (a > b) ? a : b;
+            return max;
+        }
+
+        static float[] Circle(float r)
+        {
+            float pi = 3.14f;
+            float perimeter = 2 * pi * r;
+            float area = pi * (r * r);
+            return new float[] { perimeter, area };
+        }
+        static int[] ComplexCompare(int[] a)
+        {
+            int sum = 0, min = a[0],max = a[0],avg=0;
+            for (int i = 0; i < a.Length; i++)
+            {
+                sum += a[i];
+                if (a[i] > max)
+                {
+                    max = a[i];
+                }
+                if (a[i] < min)
+                {
+                    min = a[i];
+                }
+            }
+            avg = sum / a.Length;
+            return new int[] { sum, max, min, avg };
+        }
+        static bool Primenumber(int a)
+        {
+            for (int i = 2; i < a; i++)
+            {
+                if (a % i == 0)
+                    return false;
+            }
+            return true;
+        }
+        static bool Year(int a)
+        {
+            if (a%400 == 0 || (a%4 == 0 && a%100 != 0))
+            {
+                return true;
+            }
+            return false;
+        }
+        static void Main(string[] arg)
+        {
+            Console.WriteLine("比较大小：");
+            Console.WriteLine(Compare(10, 20));
+
+            Console.WriteLine("圆：");
+            float[] circle = Circle(20);
+            Console.WriteLine("perimeter:" + circle[0] + " " + "area:" + circle[1]);
+
+            Console.WriteLine("综合：");
+            int[] x = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+            int[] result = ComplexCompare(x);
+            Console.WriteLine("总和：" + result[0] + "最大" + result[1] + "最小" + result[2] + "平均" + result[3]);
+
+            bool result2 = Primenumber(21);
+            if (result2)
+            {
+                Console.WriteLine("是质数");
+            }
+            else
+            {
+                Console.WriteLine("不是质数");
+            }
+
+            Console.WriteLine("闰年：");
+            Console.WriteLine(Year(2200));
+
+
+            
+        }
+    }
+}