gistfile1.py

#Author - Mohit Ranka

def rangify(input_list):
    """
    Takes list of integers as input and returns a string as its range representation
    """
    output_string = ""
    hold = False
    input_list = sorted(list(set(input_list)))
    prev_val = input_list[0]
    for i,curr_val in enumerate(input_list):
        if hold and curr_val!=prev_val+1:
            output_string += '-%s'%(prev_val)
        if curr_val==prev_val+1:
            hold = True
            if i==(len(input_list)-1):
                output_string+='-%s'%(curr_val)
        else:
            hold = False
            if i==0:
                output_string+='%s'%(curr_val)
            else:
                output_string+=',%s'%(curr_val)
        prev_val=curr_val
    return output_string

if __name__ == '__main__':
    assert rangify([1])=='1'
    assert rangify([1,2])=='1-2'
    assert rangify([1,2,3,4])=='1-4'
    assert rangify([1,3])=='1,3'
    assert rangify([1,7,3,3,4,8,9,10])=='1,3-4,7-10'
    assert rangify([1,2,7,3,3,4,8,9,10])=='1-4,7-10'
    assert rangify([1,4,5,6,8])=='1,4-6,8'
    assert rangify([2,3,4,5,7,8,10,11])=='2-5,7-8,10-11'
    assert rangify([2,3,4,9,5,7,8,10,11])=='2-5,7-11'
    assert rangify([6,9,4,10,98,11,100,99,94,100,97])=='4,6,9-11,94,97-100'