javabooleanboolean-logic

Check if at least two out of three booleans are true

An interviewer recently asked me this question: given three boolean variables, a, b, and c, return true if at least two out of the three are true.

My solution follows:

boolean atLeastTwo(boolean a, boolean b, boolean c) {
    if ((a && b) || (b && c) || (a && c)) {
        return true;
    }
    else{
        return false;
    }
}

He said that this can be improved further, but how?

Solution

  • Rather than writing:

    if (someExpression) {
    return true;
} else {
    return false;
}

    Write:

    return someExpression;

    As for the expression itself, something like this:

    boolean atLeastTwo(boolean a, boolean b, boolean c) {
    return a ? (b || c) : (b && c);
}

    or this (whichever you find easier to grasp):

    boolean atLeastTwo(boolean a, boolean b, boolean c) {
    return a && (b || c) || (b && c);
}

    It tests a and b exactly once, and c at most once.

    References