variable doesn't change its value in C++

I am a beginner in C++ and I’m writing a function that is supposed to find the closest point in a set of points ([x1,…xn]=positions_x,[y1,…yn]=positions_y) to a given point (x0,y0).

Here is my function:

double nearestPoint(double x, double y)
{
    double ind_min = 0;
    double xi = 0;
    double yi = 0;
    double dist_mini = 1000000;
    int i;
    for (i = 0; i < 50000; i=i+1)
        xi = positions_x[i];
        yi = positions_y[i];
        double a = pow(x-xi,2);
        double b = pow(y-yi,2);
            if (sqrt(a+b)<=dist_mini)
                dist_mini = sqrt(a+b);
                ind_min = i;
    return ind_min;
}

However, this always returns the exact same point. After investigation, it seems that the value of the "dist_mini" variable remains unchanged even if sqrt(a+b) is smaller. As a consequence, ind_min remains unchanged.

If you have any ideas it would really helpful,

Thank you

>Solution :

Add curly brackets ({ & }) to ensure all statements are executed in the for- and if-block. Without the curly brackets, only the first statement will be inside the block.

for (i = 0; i < 50000; i=i+1)
{
    xi = positions_x[i];
    yi = positions_y[i];
    double a = pow(x-xi,2);
    double b = pow(y-yi,2);
    if (sqrt(a+b)<=dist_mini)
    {
        dist_mini = sqrt(a+b);
        ind_min = i;
    }
}
return ind_min;