c++ - if语句问题？

Question

我的程序已启动并正在运行，但我的 if 语句在某处存在问题，使“scalene”成为除了正确输出之外的输出(除非 scalene 是正确的输出)。看问题:

谁能发现这个错误？

三角形函数

# include "header.h"

triangleType triangleShape(float sideLength1, float sideLength2, float sideLength3)
{
    triangleType triangle;

    if (sideLength1 + sideLength2 < sideLength3)
        triangle = noTriangle;
    else if (sideLength1 + sideLength3 < sideLength2)
        triangle = noTriangle;
    else if (sideLength3 + sideLength2 < sideLength1)
        triangle = noTriangle;
    else if (sideLength1 == sideLength2 == sideLength3)
        triangle = equilateral;
    else if (sideLength1 == sideLength2)
        triangle = isoceles;
    else if (sideLength1 == sideLength3)
        triangle = isoceles;
    else if (sideLength2 == sideLength3)
        triangle = isoceles;
    else
        triangle = scalene;

    return triangle;
}

输出函数

# include "header.h"

void output (float sideLength1, float sideLength2, float sideLength3)
{
    if (triangleShape (sideLength1, sideLength2, sideLength3) == noTriangle)
        cout << "Side lenghts of " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << " would not form a triangle." << endl;
    else if (triangleShape (sideLength1, sideLength2, sideLength3) == equilateral)
        cout << "A triangle with sides of lengths " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << "would be " <<
        "an equilateral triangle."<< endl;
    else if (triangleShape (sideLength1, sideLength2, sideLength3) == isoceles)
        cout << "A triangle with sides of lengths " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << "would be " <<
        "an isoceles triangle."<< endl;
    else (triangleShape (sideLength1, sideLength2, sideLength3) == scalene);
        cout << "A triangle with sides of lengths " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << " would be " <<
        "a scalene triangle."<< endl;
}

Answer 1

你在这一行多了一个分号:

 else (triangleShape (sideLength1, sideLength2, sideLength3) == scalene);

删除末尾的分号，并在行中添加一个if(或完全删除检查)。它导致始终出现“else”后面的打印，因为它成为一个单独的语句。

您可以执行以下任一操作:

 else if (triangleShape (sideLength1, sideLength2, sideLength3) == scalene)
    cout << "A triangle with sides of lengths " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << " would be " <<
    "a scalene triangle."<< endl;

或者:

 else // There are no other options here...
    cout << "A triangle with sides of lengths " << sideLength1 << " " << sideLength2 << " and " << sideLength3 << " would be " <<
    "a scalene triangle."<< endl;

话虽如此，您可能需要考虑运行一次您的函数并存储结果，然后对该结果进行检查(或者甚至使用 switch statement )。

---

此外，正如Blastfurnace指出的那样，你的比较不正确。你应该使用:

if ( (sideLength1 == sideLength2) && (sideLength1 == sideLength3))