多种图形求面积，这是习题。不能有一点偏差

#include <stdio.h>

#define PI 3.1415926

int main()
{
    int t;
    scanf("%d", &t);
    switch (t)
    {
    case 1:
    {
        float a, b;
        scanf("%f%f", &a, &b);
        printf("%d", (int)(a * b));
        break;
    }
    case 2:
    {
        float a, b;
        scanf("%f%f", &a, &b);
        printf("%d", (int)(a * b / 2.0f));
        break;
    }
    case 3: {
        float r;
        scanf("%f", &r);
        printf("%d", (int)(PI * r * r));
        break;
    }
    default:
        break;
    }
    return 0;
}