[英]I believe I am getting confused with the pointers in my program
下面我創建了一個進入 while 循環的函數。 在 while 循環中,調用 if 語句遍歷列表並檢查數字以查看哪個最大,哪個最小。 當我運行程序時,只調用一個printf()
,並且多次打印相同的printf()
。 似乎選擇兩個數字並在同一個printf()
函數下打印它們。我知道firstNumber = firstNumber->next;
應該遍歷列表。 是不是secondNumber = secondNumber->next->next;
應該指向列表中的下一個數字?
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;
}
}
}
完整程序的示例運行:
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
if()
內部的比較應該在值上,而不是在指針上。
if( num1 > num2) {
// Do something.
} else {
// Do something else.
}
那是因為你在執行這個firstNumber = firstNumber->next;
在while()
循環中聲明兩次。
firstNumber = firstNumber->next;
firstNumber = firstNumber->next;
這使得secondNumber == firstNumber;
你能說明結果是什么嗎?
我認為問題在於firstNumber
和secondNumber
的分配。 它們似乎確實指向同一個對象。 因此,修改一個將修改另一個。 此外,我認為跟蹤列表的頭部是安全的。 我會做這樣的事情:
void NumberSize(NewNumber *start){
if(start==NULL){
printf('empty list');
return;
}
double high = start->newNum;
double small= start->newNum;
NewNumber *iterator = start->next;
while(iterator!=NULL){
if(iterator->newNum > high){
high = iterator->newNum;
}
if(iterator->newNum < small){
small = iterator->newNum;
}
iterator = iterator->next;
}
printf("The biggest number is:%lf \n",high);
printf("The smallest number is:%lf \n",small);
}
我不確定這是否是您想要實現的目標...
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