C 编程允许在另一个循环中使用一个循环。以下部分显示了几个示例来说明该概念。
嵌套语法
C 中嵌套 for 循环语句的语法如下 -
for ( init; condition; increment ) {
for ( init; condition; increment ) {
statement(s);
}
statement(s);
}
C 语言中嵌套 while 循环语句的语法如下：
while(condition) {
while(condition) {
statement(s);
}
statement(s);
}
C 语言中嵌套 do...while 循环语句的语法如下：
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入任何其他类型的循环中。例如，“for”循环可以在“while”循环内，反之亦然。
嵌套循环示例
以下程序使用嵌套 for 循环来查找从 2 到 100 的素数 -
#include <stdio.h>
int main () {
/* 局部变量定义 */
int i, j;
for(i = 2; i<100; i++) {
</span><span class="kwd">for</span><span class="pun">(</span><span class="pln">j </span><span class="pun">=</span><span class="pln"> </span><span class="lit">2</span><span class="pun">;</span><span class="pln"> j </span><span class="pun"><=</span><span class="pln"> </span><span class="pun">(</span><span class="pln">i</span><span class="pun">/</span><span class="pln">j</span><span class="pun">);</span><span class="pln"> j</span><span class="pun">++)</span><span class="pln">
</span><span class="kwd">if</span><span class="pun">(!(</span><span class="pln">i</span><span class="pun">%</span><span class="pln">j</span><span class="pun">))</span><span class="pln"> </span><span class="kwd">break</span><span class="pun">;</span><span class="pln"> </span><span class="com">// 如果找到因子，则不是素数</span><span class="pln">
</span><span class="kwd">if</span><span class="pun">(</span><span class="pln">j </span><span class="pun">></span><span class="pln"> </span><span class="pun">(</span><span class="pln">i</span><span class="pun">/</span><span class="pln">j</span><span class="pun">))</span><span class="pln"> printf</span><span class="pun">(</span><span class="str">"%d is prime\n"</span><span class="pun">,</span><span class="pln"> i</span><span class="pun">);</span><span class="pln">
}
return 0;
}
当上面的代码被编译和执行时，它会产生以下结果 -
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
