In which segment a given number lies in? [duplicate]

Answer 1

Check the segments again after the division.

bool inSegment(double x, double l, double segment)
{
    return (x >= l*(segment-1)) && (x < l*segment);
}

int segmentId;
double segment = floor(x/l);

if (inSegment(x, l, segment-1))
    segmentId = segment - 1;
else if (inSegment(x, l, segment))
    segmentId = segment;
else if (inSegment(x, l, segment+1))
    segmentId = segment + 1;
else
    printf("Something wrong happened\n");

Or use an epsilon and round the value up if the value is close enough to an integer above.