todo

為什麼要使用電腦? 就是要用電腦重複幫我們作相同的工作. 所以迴圈是整個程式的靈魂

基本語法

for
for (初始值;條件式;增值)
計算1+2+..100
無初始值，需置於迴圈外
條件式可於迴圈內，用於複雜判斷式
增值 i++ , ++i, i–, –i 之差異

巢狀迴圈

for (int i=1;i<=5;i++){
     for (int j=1;j<=i;j++){
	Console.Write(“ {0}”,j);
     }
     Console.WriteLine();
}

while

while (判斷式){
}
判斷式有可能永遠為true, 會變成無窮迴圈，需有break退出

do…while
do{
}while(判斷式); <==需有 “;”
先作一次迴圈再判斷

break

用於for, while, switch, do

continue

continue會忽略下面的指令，直接回到迴圈第一行

直向列印

1
2
3
4
5
6
7
8
9
10

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 10; i++)
            {
                Console.WriteLine(i);
            }
        }
    }
}

橫向列印

1 2 3 4 5 6 7 8 9 10

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 10; i++)
            {
                Console.Write("{0} ", i);
            }
            Console.WriteLine();
        }
    }
}

九九乘法表

static void Main(string[] args)
{
    for (int i = 1; i <= 9; i++)
    {
        for (int j=1; j <= 9; j++)
        {
	    Console.Write("{0, 2:d} ", i * j);
        }
         Console.WriteLine();
    }
}
結果 : 
 1  2  3  4  5  6  7  8  9
 2  4  6  8 10 12 14 16 18
 3  6  9 12 15 18 21 24 27
 4  8 12 16 20 24 28 32 36
 5 10 15 20 25 30 35 40 45
 6 12 18 24 30 36 42 48 54
 7 14 21 28 35 42 49 56 63
 8 16 24 32 40 48 56 64 72
 9 18 27 36 45 54 63 72 81

左三角

*
* *
* * *
* * * *
* * * * *

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 5; i++)
            {
                for (int j = 1; j <=i; j++)
                {
                    Console.Write("* ");
                }
                Console.WriteLine();
            }
        }
    }
}

倒三角

* * * * *
* * * *
* * *
* *
*
代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 5; i++) { for (int j = 5; j >=i; j--)
                {
                    Console.Write("* ");
                }
                Console.WriteLine();
            }
        }
    }
}

右三角

        *
      * *
    * * *
  * * * *
* * * * *

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 5; i++)
            {
                for (int j = 1; j <= 5-i; j++)
                {
                    Console.Write("  ");
                }
                for (int j = 1; j <=i; j++)
                {
                    Console.Write("* ");
                }
                Console.WriteLine();
            }
        }
    }
}

偶數

< < < < <
> > > > >
< < < < <
> > > > >
< < < < <

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 5; i++)
            {
                for (int j = 1; j <=5; j++) { if(i%2==0)Console.Write("> ");
                    else Console.Write("< ");
                }
                Console.WriteLine();
            }
        }
    }
}

三條件相間

A A A A A
B B B B B
C C C C C
A A A A A
B B B B B

代碼
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i <= 5; i++)
            {
                for (int j = 1; j <=5; j++)
                {
                    if(i%3==1)Console.Write("A ");
                    else if (i%3==2) Console.Write("B ");
                    else Console.Write("C ");
                }
                Console.WriteLine();
            }
        }
    }
}