Converts an Excel column name, e.g. 'A', 'B',...'Z', 'AA', 'AB', etc. to a integer index (0-based)

ExcelColumnToIndex.groovy

int colToIndex(String col) {
    col.length() == 1 ? col.chars[0] - 65 : (col.chars[0] - 64) * Math.pow(26, col.length() - 1) + colToIndex(col.substring(1))
}

[A:0, B:1, Y:24, Z:25, AA:26, AB:27, AY:50, AZ:51, BA:52, BB:53, 
 BY:76, BZ:77, CA:78, CB:79, CY:102, CZ:103, DA:104, DB:105, 
 ZY:700, ZZ:701, AAA:702, AAB: 703, AAZ: 727, ABA: 728, AZZ: 1377, 
 BAA:1378 ].each { k, v -> 
    assert colToIndex(k) == v 
}