C++三角形面积周长计算程序传入参数后仍输出垃圾值的原因排查

Let's walk through the issues in your code step by step—they're common pitfalls, so don't worry, fixing them is straightforward:

1. You're Passing Uninitialized Variables Instead of Using Your Class's Data #

In your main() function, you declare int x, y, z; but never assign any values to them. When you call t1.Area(x, y, z) and t1.peri(x, y, z), you're passing these uninitialized variables (which hold random garbage values) instead of using the a, b, c values you already stored in your t1 object via t1.getdata().

Even worse, your peri() and Area() functions accept parameters, but you don't need them—your class already has a, b, c as member variables. You can rewrite these functions to use the class's internal data directly.

2. The Area() Function Has Two Critical Flaws #

• It doesn't return a value: The function is declared as float Area(...), but there's no return area; statement at the end. When you try to print its result in main(), you're getting undefined garbage because the function doesn't properly return the calculated area.
• Integer division messes up the semi-perimeter: s = (a + b + c) / 2; uses integer division since a, b, c are integers. For example, if your sides sum to 9, this would give you 4 instead of the correct 4.5, which breaks the Heron's formula calculation. You need to cast the sum to a float first to get a decimal result.
• Unnecessary cout inside Area(): You're printing the area twice—once inside the function and once in main(). Pick one place to avoid duplication.

Fixed Version of Your Code #

Here's the corrected code with all these issues addressed:

#include <iostream>
#include <cmath>
// Removed <conio.h> since it's non-standard and not used here
using namespace std;

class Triangle {
public:
    int a, b, c;
    void getdata();
    // Rewrote to use class members instead of parameters
    int peri() {
        return a + b + c;
    }
    float Area() {
        // Cast sum to float to avoid integer division
        float s = static_cast<float>(a + b + c) / 2;
        float area = sqrt(s * (s - a) * (s - b) * (s - c));
        return area;
    }
};

void Triangle::getdata() {
    cin >> a >> b >> c;
}

int main() {
    cout << "Enter the three sides: ";
    Triangle t1;
    t1.getdata();
    cout << "The area of that triangle is " << t1.Area() 
         << " and the perimeter is " << t1.peri() << endl;
    return 0;
}

Key Changes Explained #

• Removed unused <conio.h> header (it's not standard C++ and wasn't being used).
• Modified peri() and Area() to use the class's own a, b, c members instead of accepting external parameters.
• Fixed the semi-perimeter calculation with static_cast<float> to ensure floating-point division.
• Added return area; to the Area() function so it properly returns the calculated value.
• Removed the redundant cout inside Area() to avoid duplicate output.
• Cleaned up the output message in main() for readability.

内容的提问来源于stack exchange，提问作者Noob_coder