c - 我相信我对程序中的指针感到困惑

Question

下面我创建了一个进入 while 循环的函数。在 while 循环中，调用 if 语句来遍历列表并检查数字以查看哪个数字最大，哪个数字最小。当我运行该程序时，仅调用一个 printf() ，并且多次打印相同的 printf() 。它似乎选择两个数字并在同一个 printf() 函数下打印它们。我知道 firstNumber = firstNumber->next; 应该遍历列表。 secondNumber = secondary->next->next; 不是应该指向列表中的下一个数字吗？

typedef struct A_NewNumber {
    struct A_NewNumber *next;
    double newNum;
} NewNumber;

void NumberSize(NewNumber *start) {

    NewNumber *firstNumber = start;
    NewNumber *secondNumber = start;

    if(start != NULL) {
        while (secondNumber != NULL && secondNumber->next != NULL) {
            secondNumber = secondNumber->next->next;
            firstNumber = firstNumber->next;
            if(secondNumber > firstNumber) {
                printf("The biggest number is:%lf \n",secondNumber->newNum);
            } else {
                printf("The smallest number is:%lf \n",firstNumber->newNum);
            }
            firstNumber = firstNumber->next;
        }
    }
}

完整程序的运行示例:

 Please enter a number or
'quit' to stop or 'print' to print/calculate
12
Please enter a number or
'quit' to stop or 'print' to print/calculate
13
Please enter a number or
'quit' to stop or 'print' to print/calculate
14
Please enter a number or
'quit' to stop or 'print' to print/calculate
15
Please enter a number or
'quit' to stop or 'print' to print/calculate
16
Please enter a number or
'quit' to stop or 'print' to print/calculate
17
Please enter a number or
'quit' to stop or 'print' to print/calculate
print
Numbers:12.000000
Numbers:13.000000
Numbers:14.000000
Numbers:15.000000
Numbers:16.000000
Numbers:17.000000

The biggest number is:14.000000
The biggest number is:16.000000
The smallest number is:17.000000

Answer 1

if() 内部的比较应该基于值，而不是指针。

if( num1 > num2) {
    // Do something.
} else {
    // Do something else.
}

这是因为您在 while() 循环内执行了两次 firstNumber = firstNumber->next; 语句。

firstNumber = firstNumber->next;
firstNumber = firstNumber->next;

这使得secondNumber == firstNumber;