Comparing two strings to see if they are rotation [closed] - c++

Question

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 8 years ago.
Improve this question
Rotation means one string is created from moving the other string one or more bits to the right. For example abc and cab are rotation, abcd and bacd are not rotation.
I wrote the code below however it's failed to pass the last one test case (don't know what it is). Could anyone give me some hints about where goes wrong or is there any more efficient algorithm:
int isLetterInWord(char c, char* word)//find first letter in the word which is equal to c
{
int len = strlen(word);
for(int i=0; i<len; ++i)
{
if(c==word[i])
return i;
}
return -1;
}
int isRotation(char* word1, char* word2)
//check if word1 and word2 are rotation. if so return 1 otherwise -1
{
if(word1 == NULL && word2 == NULL)
return 1;
int len1 = strlen(word1);
int len2 = strlen(word2);
if(len1!= len2)
return -1;
for(int i=0; i<len1; ++i)
{
int pos = isLetterInWord(word1[i], word2);
if(pos == -1)
return -1;
else
{
int p1 = i, p2 = pos;
int cnt=0;
while(cnt<len1)
{
if(word1[p1++]!=word2[p2++])
break;
if(p1==len1)p1=0;
if(p2==len2)p2=0;
cnt++
}
if(cnt==len1)
return 1;
}
}
return -1;
}

Answer 1

Another algorithm of solving this question is as follow:
Lets say first string is str1 and need to check whether str2 is rotation of str1.
The algorithm is as follow:
concatanate str1 to str1. Lets call it str3.
Now check whether str2 is a sub-string of str3.
If str2 is sub-string of str3 then it is a rotation of str1 otherwise not.
Please find the function to check rotation of a string:
int Rotations(char *str1, char *str2)
{
int size1 = strlen(str1);
int size2 = strlen(str2);
char *temp;
void *ptr;
if (size1 != size2)
return 0;
temp = (char *)malloc(sizeof(char)*(size1*2 + 1));
temp[0] = '\0';
strcat(temp, str1);
strcat(temp, str1);
ptr = strstr(temp, str2);
free(temp);
if (ptr != NULL)
return 1;
else
return 0;
}

Answer 2

if(word1==NULL&&word2==NULL)
This should be
if(word1==NULL||word2==NULL)
Not gone through your logic.

Answer 3

Overview: Find first char matching char in string, Then perform xor on string, Till end of minimum length string, This way you can find whether string are rotation string of each other
Pre-Condition: Length of both strings are equal, As already stated above answers
Step 1: Find first matching char in both string notice pos(position) of char in the first string.
Step 2: Now perform xor on first string from pos to the end of first string, With substring with same length from the second string.
Step 3: If result xor is 0 means First part matches of the string matched, And proceed to match remaining part(substring), Which is first char in the first string to char at pos-1, And substring from second string from pos+1 to end of string, Then perform same xor on them,
Step 4: If that matches then exit with sucess, And if does not match then find next matching char in first string, and repeat from step 2, until reaches end of the first string