为何C语言三角形面积计算代码输出始终为0？求原因及修正方案

Hey there! Let's break down why your code is always outputting 0, and fix it up step by step.

There are two key issues causing this problem:

1. Integer Truncation from Mismatched Variable Types #

You declared c as an int (integer), but the area of a triangle is almost always a floating-point number (like 0.5 when base and height are both 1). In C, when you assign a float/double value to an integer variable, it chops off the decimal part entirely—no rounding, just straight truncation.

So if your calculation gives you 0.5, c becomes 0. Even if you input larger numbers that should give a whole number (like base=4, height=3, area=6), it might work sometimes, but any non-whole number result will get cut down to the nearest lower integer. If you're testing with small values, that's why you only see 0 every time.

On top of that, your t=0.5 is a double (floating-point), and a*b is an integer. Multiplying them gives a double, but shoving that into an int variable guarantees you'll lose decimal data.

2. A Pointless Extra Input #

That final scanf("%d",&c); does nothing useful—it just makes the program wait for another input after outputting the area, which is confusing and unnecessary.

We'll switch to a floating-point type for the area, fix the print statements, and clean up the extra bits:

#include <stdio.h>
int main(void) {
    int a, b;
    double c; // Use double to store the floating-point area
    printf("Enter the height of the triangle: ");
    scanf("%d", &a);
    printf("Enter the base of the triangle: ");
    scanf("%d", &b);
    c = 0.5 * a * b; // No need for a separate t variable—compute directly
    printf("The area of the triangle: %.2f\n", c); // %.2f shows 2 decimal places for clarity
    return 0;
}

• Your original printf lines (like printf("Get the height of the triangle",a);) had an extra a parameter that didn't do anything—since there's no %d placeholder in the string, C ignores it. The fixed code removes that.
• Play with the printf format if you want: use %f for default precision, or %.1f to show just one decimal place.
• For robustness, you could add checks to make sure the user enters positive numbers (since a triangle can't have a negative base or height!).

内容的提问来源于stack exchange，提问作者Xander ovrload