Question

我很难使用while循环从起始数字100开始倒数。我需要以5递增倒数，并显示每个结果，直到达到20。

#include <stdio.h>

void count_down( void ) {

    // Declare an integer variable that you will use to count. Initially 
    //     the counter should equal the start value, 100.
    int counter = 100;
    printf(counter);
    // Begin a WHILE statement that will execute its loop body if the counter 
    // is greater than the end value, 20.

    while (counter < 20) {
        // Print the value of the counter on a line by itself.
        printf(counter);
        // Subtract 5 from the counter.
        int new_number = counter - 5;
        printf(new_number);
    }
}


int main( void ) {
    count_down();
    return 0;
}

Answer 1

该函数的主要问题是将count设置为100，然后尝试进入一个永远不会激活的循环while（100永远不会小于20）。如果要进入此循环，则循环内没有指令会真正更改循环条件变量，因此它将无限运行。

除此之外，我建议向函数中添加参数以使其可用于任何倒数计时和任何步骤：

#include <stdio.h>

void count_down(int start, int end, int step) {
    while (start >= end) {
        printf("%d\n", start);
        start -= step;
    }
}

int main() {
    count_down(100, 20, 5);
    return 0;
}

输出：

这是一个repl。

Answer 2

两件事：

修正while条件：您只对20以上的数字感兴趣
您需要减少计数器变量。

查看以下更改：

while (counter > 20) {
    // Subtract 5 from the counter.
    counter -= 5;
    // Print the value of the counter on a line by itself.
    printf("%d\n", counter);
}

Answer 3

尽管其他答案已就如何解决您的方法提出了意见，但应注意，while循环比for循环更合适，因为它是为此目的而设计的。

for(int counter = 100; counter >= 20; counter -= 5) {
    printf("%d\n", counter);
}

Answer 4

似乎，您永远不会更改counter的值，而while内的条件似乎是错误的。尝试：

#include <stdio.h>

void count_down( void ) {

    // Declare an integer variable that you will use to count. Initially 
    //     the counter should equal the start value, 100.
    int counter = 100;
    printf(counter);
    // (c) Begin a WHILE statement that will execute its loop body if the 
    //     counter is greater than the end value, 20.
    while (counter > 20) {
        // Print the value of the counter on a line by itself.
        printf(counter);
        // Subtract 5 from the counter.
        counter = counter - 5;
        printf(counter);
    }
}


int main( void ) {
    count_down();
    return 0;
}

Answer 5

您可以尝试以下方法：

#include <stdio.h>

void count_down(int counter) {

 // Declare an integer variable that you will use to count. Initially 
 //     the counter should equal the start value, 100.
printf("%d\n", counter);
// Begin a WHILE statement that will execute its loop body if the counter 
// is greater than the end value, 20.

while (counter > 20) {
    // Print the value of the counter on a line by itself.

    // Subtract 5 from the counter.
    counter = counter - 5;
   printf("%d\n", counter);
}
}


int main( void ) {
count_down(100);
return 0;
}

以5递增计数

5 个答案:

输出：