C# - 嵌套循环

C# 允许在一个循环内使用另一个循环。以下部分显示了一些示例来说明此概念。

语法

C# 中嵌套 for 循环语句的语法如下所示：

for ( init; condition; increment ) {
   for ( init; condition; increment ) {
      statement(s);
   }
   statement(s);
}

C# 中嵌套 while 循环语句的语法如下所示：

while(condition) {
   while(condition) {
      statement(s);
   }
   statement(s);
}

C# 中嵌套 do...while 循环语句的语法如下所示：

do {
   statement(s);
   do {
      statement(s);
   }
   while( condition );
}
while( condition );

关于循环嵌套的最后一点是，您可以将任何类型的循环放在任何其他类型的循环内。例如，for 循环可以在 while 循环内，反之亦然。

示例

以下程序使用嵌套 for 循环查找 2 到 100 之间的素数：

using System;

namespace Loops {
   class Program {
      static void Main(string[] args) {
         /* local variable definition */
         int i, j;
         
         for (i = 2; i < 100; i++) {
            for (j = 2; j <= (i / j); j++)
            if ((i % j) == 0) break; // if factor found, not prime
            if (j > (i / j)) Console.WriteLine("{0} is prime", i);
         }
         Console.ReadLine();
      }
   }
} 

编译并执行上述代码后，将产生以下结果：

2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime