Question

I have the following code in C:

#define CONST 1200
int a = 900;
int b = 1050;
int c = 1400;

if (A_CLOSEST_TO_CONST) {
  // do something
}

What is a convenient way to check whether if a is the closest value to CONST among a,b and c ?

Edit:

It doesn’t matter if I have 3 variables or an array like this (it could be more than 3 elements):

int values[3] = {900, 1050, 1400};

Answer 1

This works for three variables:

if (abs(a - CONST) <= abs(b - CONST) && abs(a - CONST) <= abs(c - CONST)) {
    // a is the closest
}

This works with an array of one or more elements, where n is the number of elements:

int is_first_closest(int values[], int n) {
    int dist = abs(values[0] - CONST);
    for (int i = 1; i < n; ++i) {
        if (abs(values[i] - CONST) < dist) {
            return 0;
        }
    }
    return 1;
}

See it working online: ideone