找出字符串中连续相同字母的最长子串

之前腾讯二面的一道机试题，比如‘aafsdeeecccccdfeec’，连续相同的最长子串为‘ccccc’

string = input("input string:")
a = string + ' '
b = [a[0], 1]
count = 1

for i in range(0, len(a)-1):
    if a[i] == a[i+1]:
        count += 1
    elif int(b[1]) < count:
        b.clear()
        b += [a[i], count]
        count = 1
    else:
        count = 1

print(b[0]*b[1])