Question

我刚刚进入C，我遇到了一些麻烦。我有一点时间弄清楚为什么这个while循环不会重复。我在JavaScript中创建了相同的循环，并重复输出正确的输出。 http://jsfiddle.net/rFghh/

如果我使用while (cents >= 25)，则终端打印起始硬币并挂起只是闪烁。如果我使用<=25（如下所示），则会打印一次迭代。关于我做错了什么的想法？

/**
 * Greedy, given a change amount, figures out the min number of coins needed
 */

#include <stdio.h>
#include <cs50.h>
#include <math.h>

int main(int argc, char const *argv[])
{
    // declare variables
    int cents = 0;
    int coins = 0;

    // ask user for amount of money, accepts a float value
    // convert input to cents and round to nearest int
    printf("O hai! ");
    do 
    {
        printf("How much change is owed? ");
        cents = round(100 * GetFloat());
    // if input is negative then ask again
    } while (cents <= 0);

    printf("Starting Cents: %d, coins are: %d\n", cents, coins);

    // Check if you can use a quarter
    while (cents <= 25);
    {
        printf("Cents before decrement: %d\n", cents);
        cents = cents - 25;
        printf("Cents after decrement: %d\n", cents);
        coins = coins + 1;
    }

    printf("FINAL Cents: %d, coins are: %d\n", cents, coins);

    return 0;
}



jharvard@appliance (~/cs50/Week_1/pset1): make greedy && ./greedy
clang -ggdb3 -O0 -std=c99 -Wall -Werror    greedy.c  -lcs50 -lm -o greedy
O hai! How much change is owed? 1.25
Starting Cents: 125, coins are: 0
Cents before decrement: 125
Cents after decrement: 100
FINAL Cents: 100, coins are: 1
jharvard@appliance (~/cs50/Week_1/pset1):

Answer 1

代码没有按照您的想法执行。这一行：

while (cents <= 25);
{ ::: }

相当于：

while (cents <= 25)
{
    ;
}
{ ::: }

这将永远迭代执行永不改变cents的空语句。通过删除分号并重新评估逻辑来修复它。

Answer 2

while声明末尾有一个分号： -

while (cents <= 25);  <-- Here's the semi-colon. Remove it.

Answer 3

您的季度检查需要修复。这实际上可能是一个单独的功能，但快速修复将是：

while (cents >= 25)  //should be greater than or equal to and get rid of semicolon 
{
    printf("Cents before decrement: %d\n", cents);
    cents = cents - 25;
    printf("Cents after decrement: %d\n", cents);
    coins++;
}

为什么我的while循环不会在C中重复？

3 个答案: