c - C中的循环。程序中的第一个循环不起作用并且是无限的

Question

我不明白为什么第一个循环不起作用。即使填充的欠 float 实际上大于 0，这也是一个无限循环。为什么循环不起作用？

#import <cs50.h> 
#import <stdio.h>

int main(void)
{
    float owed = -1 ;

    while (owed < 0) 
    {
        printf("O hai! How much change is owed?\n") ;
        float owed = GetFloat() ;
        owed = owed * 100 ;
    }

    int coins = 0 ;

    while (owed >= 25)
    {
        owed = owed - 25 ;
        coins = coins + 1 ;
    }

    while (owed >= 10)
    {
        owed = owed - 10 ;
        coins = coins + 1 ;
    }

    while (owed >= 5)
    {
        owed = owed - 5 ;
        coins = coins + 1 ;
    }

    while (owed >= 1) 
    {
        owed = owed - 1 ;
        coins = coins + 1 ;
    }

    printf("%i\n", coins) ;
}

Answer 1

你需要改变

float owed = GetFloat() ;

至

owed = GetFloat() ;

因为您有两个不同范围的欠。 (您不会更改外部!)

编辑

PS: 您可以更改代码:

while (owed >= 25)
{
    owed = owed - 25 ;
    coins = coins + 1 ;
}

至

int new_coins = ((int)owed)/25;
coins += new_coins;
owed = owed - 25.0f * new_coins;