CATEGORY:
    MITRE CWE-193: Off-by-one error.
    
REFERENCE: 
    http://cwe.mitre.org/data/definitions/193.html. 

EXPLANATION:
    When a color different to the previous color terminates the current series,
    the variable currentSeriesLength is incorrectly reset to 0. It should be
    set to 1 as the new color already constitues a series of length 1.

CONSEQUENCES:
    All series following the first series will have a length that is short by
    one.

BUGFIX:
    The most straightforward fix is to set currentSeriesLength to 1 when a spin
    yields a new color:

    // New color, series terminated.
    } else {
        // Keep track of how often a particular series length (of previous
        // color) occurred.
        ++seriesMaps[prevColor][currentSeriesLength];
        // Current series is over.
        currentSeriesLength = 1  // New color has already appeared once.
    }

REMARKS:
    Off-by-one errors are among the most frequently encountered errors in
    software programs; they usually appear at the boundaries of ranges. 

    Even though this bug looks obvious in hindsight, it is somewhat shadowed by
    the fact that currentSeriesLength is initially -- and correctly -- set to 0
    upon the first loop iteration:

    // Initialize upon first spin.
    if (!initialized) {
        prevColor = newColor
        currentSeriesLength = 0
        initialized = true
    }