当你上次设法修复我的代码时，我想再次请求你的帮助。
由于我已经有一个包含五个元素的预定义列表，因此这个代码似乎是非常无关紧要的，因为没有检查列表是否为空的目的。我似乎无法找出绕过if-else的人，只需保留＆＃34;插入＆＃34;函数而不是检查列表是否为空......
#include <iostream>
#include <cmath>
using namespace std;
struct node
{
string nameOfFood;
int eatCalories;
int number;
node *next;
};
bool isEmpty(node *head);
char menu();
void insertAsFirstElement(node *&head, node *&last, string name, int eatCalories);
void insert(node *&head, node *&last, string name, int eatCalories);
void showList(node *current);
bool isEmpty(node *head)
{
if(head == NULL)
return true;
else
return false;
}
char menu()
{
char choice;
cout << "Menu\n";
cout << "1. Add food, beverage etc.\n";
cout << "2. Show the list of food(s), beverage(s) etc.\n";
cout << "3. Update your current weight\n";
cout << "4. What have you been eaten?\n";
cout << "5. What exercise have you done?\n";
cout << "6. Exit program \n";
cin >> choice;
return choice;
}
void insertAsFirstElement(node *&head, node *&last, string nameOfFood, int eatCalories)
{
node *temp = new node;
temp->nameOfFood = nameOfFood;
temp->eatCalories = eatCalories;
temp->next = NULL;
head = temp;
last = temp;
}
void insert(node *&head, node *&last, string nameOfFood, int eatCalories)
{
if(isEmpty(head))
insertAsFirstElement(head, last, nameOfFood, eatCalories);
else
{
node *temp = new node;
temp->nameOfFood = nameOfFood;
temp->eatCalories = eatCalories;
temp->next = NULL;
last->next = temp;
last = temp;
}
}
如果您需要更多代码，请告诉我？
希望得到你的帮助！
答案 0 :(得分：2)
该检查是必要的，因为如果您的列表为空，则必须执行仅在该情况下执行的特定数量的操作。
实现自己的链表真的没有用处。标准已经定义了比您的更灵活的类，请参阅std::forward_list（单链表）和std::list（双链表）。
建议您在选择容器时默认为std::vector或std::array。在这种情况下，如果您只有一个包含5个元素的列表，只需使用std::array和自定义类型：
struct food
{
string nameOfFood;
int eatCalories;
int number;
};
然后：
std::array<food, 5> food_list { ... };
答案 1 :(得分：0)
但是我的列表永远不会是空的，因为我有五个预定义的元素。我会发布剩下的代码，也许你会明白我的意思？或者，我错了。
#include <iostream>
#include <cmath>
using namespace std;
struct node
{
string nameOfFood;
int eatCalories;
int number;
node *next;
};
bool isEmpty(node *head);
char menu();
void insertAsFirstElement(node *&head, node *&last, string name, int eatCalories);
void insert(node *&head, node *&last, string name, int eatCalories);
void showList(node *current);
bool isEmpty(node *head)
{
if(head == NULL)
return true;
else
return false;
}
char menu()
{
char choice;
cout << "Menu\n";
cout << "1. Add food, beverage etc.\n";
cout << "2. Show the list of food(s), beverage(s) etc.\n";
cout << "3. Update your current weight\n";
cout << "4. What have you been eaten?\n";
cout << "5. What exercise have you done?\n";
cout << "6. Exit program \n";
cin >> choice;
return choice;
}
void insertAsFirstElement(node *&head, node *&last, string nameOfFood, int eatCalories)
{
node *temp = new node;
temp->nameOfFood = nameOfFood;
temp->eatCalories = eatCalories;
temp->next = NULL;
head = temp;
last = temp;
}
void insert(node *&head, node *&last, string nameOfFood, int eatCalories)
{
if(isEmpty(head))
insertAsFirstElement(head, last, nameOfFood, eatCalories);
else
{
node *temp = new node;
temp->nameOfFood = nameOfFood;
temp->eatCalories = eatCalories;
temp->next = NULL;
last->next = temp;
last = temp;
}
}
void showList(node *current)
{
if(isEmpty(current))
cout << "The list of foods is empty\n";
else
{
cout << "The list of foods contain: \n";
int number = 0;
while(current != NULL)
{
++number;
cout << number << " " << current->nameOfFood << " " << current->eatCalories << " calories" << endl;
current = current->next;
}
}
}
node* subtractCalories(node *head)
{
int choice;
showList(head);
cout << "Pick the food, beverage etc. from the list by number\n";
cin >> choice;
int number = 1;
node *current = head;
while (current != NULL && choice != number)
{
++number;
current = current->next;
}
cout << "You have choosen: " << current->nameOfFood << endl;
return current;
}
int main(int argc, const char * argv[]) {
double caloriesToBurn;
double weight;
double height;
double BMI;
int answerWhile = 1;
int answerToExercise = 0;
float minutesExerciseInHour;
float caloriesBurned;
node *head = NULL;
node *last = NULL;
node *current;
char choice;
int eatCalories;
string nameOfFood;
insert(head, last, "Tuna (in oil)", 190);
insert(head, last, "Milkchocolate (Marabou)", 540);
insert(head, last, "Milk (skimmed)", 33 );
insert(head, last, "Ice Tea (white peach)", 1);
insert(head, last, "Peanuts (roasted and salted)", 624);
cout << "*** Welcome to the calorie calculator! ***\n";
cout << "To get started, i need some numbers from you\n";
cout << "Please enter the number of calories you need to burn today:\n";
cin >> caloriesToBurn;
cout << "What are your current weight? (please enter in kilograms)\n";
cin >> weight;
cout << "And lastly i need to know your height (please enter in centimeters)\n";
cin >> height;
BMI = (weight / pow(height/100,2));
cout << "Your BMI is: " << BMI << endl;
if (BMI <= 18.5)
cout << "You are in the range: under weight" << endl;
else if ((BMI > 18.5) && (BMI < 25))
cout << "You are in the range: normal weight" << endl;
else
cout << "You are in the range: over weight" << endl;
do{
choice = menu();
switch(choice)
{
case '1':
cout << "Enter the name of the food, beverage etc.:";
cin >> nameOfFood;
cout << "How many calories did it contain? (measured per 100 grams):";
cin >> eatCalories;
insert(head, last, nameOfFood, eatCalories);
break;
case '2': showList(head);
break;
case '3': cout << "What you wanna update your weight to?\n";
cin >> weight;
cout << "Your weight have been update to: \n";
cout << weight << endl;
if (BMI <= 18.5)
cout << "You are in the range: under weight" << endl;
else if ((BMI > 18.5) && (BMI < 25))
cout << "You are in the range: normal weight" << endl;
else
cout << "You are in the range: over weight" << endl;
break;
case '4':
cout << endl << "You need to consume " << caloriesToBurn << " calories today!" << endl << endl;
current = subtractCalories(head);
caloriesToBurn = caloriesToBurn-current->eatCalories;
cout << endl << "You need to eat " << caloriesToBurn << " calories more today!" << endl;
break;
case '5':
do
{
cout << "How many minuttes have you ben exercising (please enter in hours)\n";
cin >> minutesExerciseInHour;
cout << "What type of exercise have you been doing?" <<endl;
cout << "1. Running" <<endl;
cout << "2. Swimming" <<endl;
cout << "3. Cycling" <<endl;
cin >> answerToExercise;
switch(answerToExercise)
{
case 1:
caloriesBurned = weight*7.5*minutesExerciseInHour;
cout << "You have burned: " << caloriesBurned << "calories\n";
caloriesToBurn = caloriesToBurn + caloriesBurned;
cout << "You have: " << caloriesToBurn << " left today\n";
break;
case 2:
caloriesBurned = weight*7*minutesExerciseInHour;
cout << "You have burned: " << caloriesBurned << "calories\n";
caloriesToBurn = caloriesToBurn + caloriesBurned;
cout << "You have: " << caloriesToBurn << " left today\n";
break;
case 3:
caloriesBurned = weight*6*minutesExerciseInHour;
cout << "You have burned: " << caloriesBurned << "calories\n";
caloriesToBurn = caloriesToBurn + caloriesBurned;
cout << "You have: " << caloriesToBurn << " left today\n";
break;
default: cout << "I think something went wrong? Try again..";
}
}
while (answerWhile != 1);
default: cout << "System exit\n";
}
}while(choice != '6');
return 0;
}
答案 2 :(得分：0)
我想我理解检查空列表 - 因此我会将我的代码带到另一个问题。
我得到了InsertAsFirstElement函数，但此刻，我想我已经忘记了函数的功能，因为在代码中没有任何地方会有＆＃34;插入第一个元素＆＃34;所以有人可以告诉那是什么功能吗？
很抱歉给您带来不便！