var TEST = function () {
    return {
        exec: function (str, rowNum) {
            
            if (rowNum === 1) { return str; }
            
            let wordRecord = new Array(rowNum);
            wordRecord.fill('');
            
            let rowPtr = 0, rowInc = -1, wordPtr = -1, bot = rowNum-1;
            while (str[++wordPtr]) {
                wordRecord[rowPtr] += str[wordPtr];
                if (rowPtr === bot || rowPtr === 0) {
                    rowInc = rowInc * -1;
                }
                rowPtr += rowInc;
            }
            
            return wordRecord.join('');
        
        }
    };
}();