CC 1.8

isRotation.py

#cc 1.8 Assume you have a method isSubstring which checks if one word is a substring of another. Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 using only one call to isSubstring (e.g.,"waterbottle"is a rotation of"erbottlewat").


def isRotation(s1, s2):

    if (len(s1) == len(s2) and len(s1) > 0):
        s = s1 + s1
        return isSubstring(s, s2)
    else:
        return False 

def isSubstring(s1, s2):
    
    if (len(s1) > 0 and len(s1) > len(s2)):
        for i in range(len(s1)):
            k = i
            j = 0
            while s2[j] == s1[k]:
                k += 1
                j += 1
                if (k == len(s1) or j == len(s2)):
                    return True
                    break
        else:
            return False        
                


s1 = 'waterbottle'
s2 = 'terbott'
print 's1',s1, 's2', s2
print'Is s2 substring of s1:', isSubstring(s1, s2)
print 'Is s2 rotation of s1:', isRotation(s1, s2)