approxpi_area.c

#include <stdio.h>
#include <math.h>

int main()
{
    int n = 100000;
    double size = 1.0 / n;
    double area = 0.0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            double x = i * size + size / 2;
            double y = j * size + size / 2;
            double r = pow(x, 2.0) + pow(y, 2.0);
            if (r <= 1)
            {
                area = area + (size * size);
            }
        }
    }
    printf("%.15f", area*4);
    return 0;
}