Java – Check if at least two out of three booleans are true

booleanboolean-logicjava

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?

Best 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

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