c++ - 需要一些帮助在我的程序中发现逻辑错误

我正在通过Bjarne Stroustrup的“使用C ++编程原理和实践”第二版来学习C ++。我致力于进行所有的练习和练习，因为我要在一个月内在学校上一门游戏AI课，而且我需要了解C ++，并且我想尽可能地了解。

无论如何，如果有人曾经做过本书中的练习，那么我就是第4章的练习。我在最后。最终产品应该是一个程序，它在while循环中采用一个数字，后跟一个度量单位（cm，in，ft或m），同时跟踪最大，最小和总和。单位以米为单位。除了将最大值和最小值转换为仪表以检查哪个更大，然后按用户最初输入的值存储之外，我完全用仪表工作。数字也插入到向量中，直到最后才对值进行排序并按顺序打印它们。

无论如何，跟踪总仪表似乎没有问题，因为它可以在末尾正确打印出来，但是当涉及到最小值时，似乎有时会出现问题，有时还会出现最大值。另外，某些值在值向量中完全不可用。我将在下面的代码。我认为该错误出在我的toMeters（）中，但我盯着它看了很长时间，以至于觉得新的一双眼睛可能会有所帮助。谢谢！

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>

using namespace std;

constexpr double mToCm = 100.00; //1m == 100cm
constexpr double inToCm = 2.54; //1in == 2.54cm
constexpr double ftToIn = 12.00; //1ft == 12in

//this function just increases total ammount of units in meters
double adder(string unit, double total, double num)
{
    if(unit == "cm")
    {
        total += (num / mToCm);
    }
    else if(unit == "in")
    {
        double temp;
        temp = num * inToCm;
        total += (temp / mToCm);
    }
    else if(unit == "ft")
    {
        double temp;
        temp = num * ftToIn;
        temp *= inToCm;
        total += (temp / mToCm);
    }
    else
    {
        total += num;
    }
    return total;
}

double toMeters(string unit, double num)
{
    double value = num;

    if(unit == "cm")
    {
        value /= mToCm;
    }
    else if(unit == "in")
    {
        value *= inToCm;
        value /= mToCm;
    }
    else if(unit == "ft")
    {
        value *= ftToIn;
        value *= inToCm;
        value /= mToCm;
    }
    return value;
}

int main()
{

    double num, biggest, smallest; //current number, biggest and smallest value
    double total = 0; //total number in meters
    string unit, biggestUnit, smallestUnit; //current unit, unit for biggest and smallest value
    int count = 0; //count for the loop it's only real purpose is on the first and second loop runs
    vector<double>meters; //a vector of doubles called meters


    cout << "Total ammount of units will be converted to meters, largest and biggest values will be kept in original units\n";
    cout << "Start of by entering a number followed by cm, m, in, ft and continue until you want to stop; to stop, press |\n";

    while(cin >> num >> unit)
    {
        //check if user want to stop
        if(num == '|')
        {
            break;
        }

        //check for correct units, if not then break out
        if(unit != "cm" && unit != "m" && unit != "in" && unit != "ft")
        {
            cout << "Unit not recognized; only cm, m, in, ft are valid\n";
            return 1;
        }
        //this checks if there is no second unit but since cin reads no
        //whitespace it doesn't work. I just haven't gotten around to removing it
        else if(unit == " ")
        {
            cout << "Please input a unit\n";
            return 1;
        }

        //all values in vectors are supposed to be in meters. If the unit is not
        //in meters, we will call a push back on the value returned by converting
        //the orignal number to meters
        if(unit != "m")
        {
            meters.push_back(toMeters(unit, num));
        }
        //else, just call a push_back
        else
        {
            meters.push_back(num);
        }

        //if the count is 0, i.e. very first run of the program, biggest and
        //smallest is equal to original and call adder() to increment the total
        if(count == 0)
        {
            biggest = smallest = num;
            biggestUnit = smallestUnit = unit;

            total = adder(unit, total, num);
        }
        //else, if count is > 0, i.e. this is not the first run, do this part
        else
        {
            //if the value returned after running toMeters on the current value
            //is greater than the biggest, biggest now equals current num and
            //biggest unit is equal to current unit. Then call adder to inceare total
            if(toMeters(unit, num) > toMeters(biggestUnit, biggest))
            {
                biggest = num;
                biggestUnit = unit;

                total = adder(unit, total, num);
            }
            //same as top function but for smallers value
            else if(toMeters(unit, num) < toMeters(smallestUnit, smallest))
            {
                smallest = num;
                smallestUnit = unit;

                total = adder(unit, total, num);
            }
            //else both numbers are equal so just make a call to adder()
            else
            {
                total = adder(unit, total, num);
            }
        }
        //increase count just because. It was really only needed to be incremented once
        ++count;
    }

    //call sort on the vector then print out the total units followed by bigges the smallest values
    //then the values in meters, is ascending sorted order.
    sort(meters.begin(), meters.end());
    cout << "Total units in meters is " << total << "\n";
    cout << "Largest unit is " << biggest << biggestUnit << "\n";
    cout << "Smallest unit is " << smallest << smallestUnit << "\n";
    cout<< "Here are all values you entered, in meters, in ascending order: \n";

    for(int i : meters)
    {
        cout << meters[i] << "m" << " ";
    }
    cout << "\n";
}

我最新的输入是1 cm 2 in 3 m 4 ft，输出是
     以米为单位的总单位是4.28
     最大单位是3m（正确）
     最小单位为2英寸（应为1厘米）
     这是您输入的所有值，以米为单位，以升序排列：
     0.01m 0.01m 0.0508m 3m

最佳答案

在第一个输入上设置biggestUnit和smallestUnit时，无需设置biggest或smallest。因此，比较无法正常进行。

尝试：

    //if the count is 0, i.e. very first run of the program, biggest and
    //smallest is equal to original and call adder() to increment the total
    if(count == 0)
    {
        biggest = smallest = num;
        biggestUnit = smallestUnit = unit;

        total = adder(unit, total, num);
    }

另外，在每个代码路径中都放置total = adder(unit, total, num);并不是一个好主意。只需将其放置在if之外。否则，很难看到每个输入总是精确地执行一次。

关于c++ - 需要一些帮助在我的程序中发现逻辑错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/45850753/