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我刚刚进入C，我遇到了一些麻烦。我花了很长时间弄清楚为什么这个 while 循环不会重复。我在 JavaScript 中做了同样的循环，它重复了正确的输出。http://jsfiddle.net/rFghh/

如果我使用while (cents >= 25)，那么终端会打印起始硬币并挂起只是闪烁。如果我使用<=25（如下）它会打印一次迭代。关于我做错了什么有什么想法吗？

/**
 * 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):
4

3 回答 3

8

代码没有做你认为它做的事情。这一行：

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

相当于：

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

所以这将永远迭代执行一个永远不会改变的空语句cents。通过删除分号并重新评估您的逻辑来修复它。

于 2013-01-18T20:17:24.433 回答
7

while语句末尾有一个分号：-

while (cents <= 25);  <-- Here's the semi-colon. Remove it.
于 2013-01-18T20:17:11.327 回答
1

您的季度支票需要修正。这实际上应该是一个单独的函数，但快速修复是：

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++;
}
于 2013-01-18T20:27:04.183 回答