C ++中的指针和函数

Question

我的程序有两个功能。一个计算可以分为美元金额的票据类型，另一个用于显示金额。

来自Java背景我不太了解C ++语法，并希望得到一些帮助。

#include <iostream>
#include <iomanip>
using namespace std;

//function declaration
void ​​calcChange​​(int amount, int* twenties, int* tens, int* fives, int*ones);
void ​​showChange​​(int amount, int twenties, int tens, int fives, int ones);

int main() {

//Declaration
int amount =0;

//Call to function
calcChange​​(&twenties, &tens, &fives, &ones);

showChange(twenties,tens,fives,ones);
do {

    cout << "Enter amount (or negative to terminate):" << endl;
    cin >> amount;


    //if loop that ans if 0 is invalid output
    if (amount == 0) {
    cout << "Invalid dollar amount.\n";
}


    //put output here
   cout << "Amount "  << setw(2) << "Twenties " << setw(2) << "Tens " << setw(5) <<"fives "<< setw(5) <<"Ones "<< endl;

   cout << amount  << setw(2) << twenties << setw(2) << tens << setw(5) << fives << setw(5) << ones << endl;


}while (amount >= 0);
    cout << "Goodbye!";
    return 0;
}

//function declarations
void ​​calcChange​​(int amount, int* twenties, int* tens, int* fives, int* ones) 
{
    while(amount >= 20){
        *twenties = amount/20;amount % 20;
        amount = *twenties;
        twenties++;
    }

    while(amount >=10){
        *tens = amount/10; amount % 10;
        amount=*tens;
        tens++;
    }

    while(amount >=5){
        *fives = amount/5; amount % 5;
        amount = *fives;
        fives++;
    }

    while(amount >=1){
        *ones = amount/1; amount % 1;
        amount = *ones;
        ones++;
    }

    return;
}


void ​​showChange​​(int amount, int twenties, int tens, int fives, int ones) {

    twenties = twenties;
    tens = tens;
    fives = fives;
    ones = ones;
    return;
}

Answer 1

首先，不确定你想用showChange做什么

功能声明

void calcChange(int amount, int* twenties, int* tens, int* fives, int* ones);

函数定义（不是声明）

void calcChange(int amount, int* twenties, int* tens, int* fives, int* ones) 
{
    *twenties = amount / 20;  amount %= 20;
    *tens = amount / 10;      amount %= 10; 
    *fives = amount / 5;      amount %= 5;
    *ones = amount / 1;       amount %= 1;
    return;
}

主功能

int main() {
    int amount = 0;
    do {
        cout << "Enter amount (or negative to terminate):" << endl;
        cin >> amount;

        if (amount == 0) {
            cout << "Invalid dollar amount.\n";
            break;
        }

        int twenties, tens, fives, ones;
        calcChange(amount, &twenties, &tens, &fives, &ones);

        cout << "Amount "  << setw(2) << "Twenties " << setw(2) << "Tens " << setw(5) <<"fives "<< setw(5) <<"Ones "<< endl;
        cout << amount  << setw(2) << twenties << setw(2) << tens << setw(5) << fives << setw(5) << ones << endl;
    } while (amount >= 0);
    cout << "Goodbye!";
    return 0;
}

Answer 2

大多数正确的代码都在那里，它只需要安排和排序更具可读性。以下是您的问题的MVC示例，如果您对代码中的某些内容有任何具体问题，请询问。

#include <iostream>
#include <iomanip>

using namespace std;

// function declaration
void calcChange(int amount, int* twenties, int* tens, int* fives, int* ones);
void showChange(int amount, int twenties, int tens, int fives, int ones);

int main()
{
    // Declarations
    int amount = 0;
    int twenties = 0;
    int tens = 0;
    int fives = 0;
    int ones = 0;
    do {
        cout << "Enter amount (or negative to terminate) " << endl;
        cin >> amount;
        // if loop that ans if 0 is invalid output
        if (amount == 0) {
            cout << "Invalid dollar amount" << endl;
            continue;
        }
        if (amount < 0) {
            break;
        }
        calcChange(amount, &twenties, &tens, &fives, &ones);
        // show output here
        showChange(amount, twenties, tens, fives, ones);
    } while (amount >= 0);
    cout << "Goodbye!" << endl;
    return 0;
}

void calcChange(int amount, int* twenties, int* tens, int* fives, int* ones) {
    *twenties = amount / 20;
    amount = amount % 20;
    *tens = amount / 10;
    amount = amount % 10;
    *fives = amount / 5;
    amount = amount % 5;
    *ones = amount;
    return;
}
void showChange(int amount, int twenties, int tens, int fives, int ones) {
    cout << "Amount: " << setw(10) << "Twenties: " << setw(10) << "Tens: " << setw(10) << "Fives:" << setw(10) << "Ones:" << setw(10) << endl;
    cout << setw(15) << twenties << setw(10) << tens << setw(10) << fives << setw(10) << ones << setw(10) << endl;
    return;
}