Rotation Groups - Amazon Top Interview Questions


Problem Statement :


A rotation group for a string contains all of its unique rotations. For example, "123" can be rotated to "231" and "312" and they are all in the same rotation group.

Given a list of strings words, group each word by their rotation group, and return the total number of groups.


Constraints

n ≤ 200 where n is the length of words.


Example 1

Input

words = ["abc", "xy", "yx", "z", "bca"]


Output

3


Explanation

There are three rotation groups:

["abc", "bca"]
["xy", "yx"]
["z"]


Solution :



title-img 




                        Solution in C++ :

int solve(vector<string>& words) {
    unordered_set<string> vis;

    for (string& s : words) {
        for (int i = 0; i < s.size(); i++) {
            rotate(s.begin(), s.begin() + 1, s.end());
            if (vis.count(s)) break;
        }
        vis.insert(s);
    }

    return vis.size();
}
                    


                        Solution in Java :

import java.util.*;

class Solution {
    public int solve(String[] words) {
        ArrayList<String> set = new ArrayList<>();
        for (String word : words) {
            boolean exist = false;
            for (String rotation : set) {
                if (rotation.length() == word.length() * 2 && rotation.contains(word)) {
                    exist = true;
                    break;
                }
            }
            if (!exist) {
                set.add(word + word);
            }
        }
        return set.size();
    }
}
                    


                        Solution in Python : 
                            
class Solution:
    def solve(self, words):
        s = set()
        for ind in range(len(words)):
            c = words[ind]

            for i in s:
                if len(c) == len(i) and c in i * 2:
                    break
            else:
                s.add(c)
        return len(s)


View More Similar Problems

Kindergarten Adventures

Meera teaches a class of n students, and every day in her classroom is an adventure. Today is drawing day! The students are sitting around a round table, and they are numbered from 1 to n in the clockwise direction. This means that the students are numbered 1, 2, 3, . . . , n-1, n, and students 1 and n are sitting next to each other. After letting the students draw for a certain period of ti

View Solution →

Mr. X and His Shots

A cricket match is going to be held. The field is represented by a 1D plane. A cricketer, Mr. X has N favorite shots. Each shot has a particular range. The range of the ith shot is from Ai to Bi. That means his favorite shot can be anywhere in this range. Each player on the opposite team can field only in a particular range. Player i can field from Ci to Di. You are given the N favorite shots of M

View Solution →

Jim and the Skyscrapers

Jim has invented a new flying object called HZ42. HZ42 is like a broom and can only fly horizontally, independent of the environment. One day, Jim started his flight from Dubai's highest skyscraper, traveled some distance and landed on another skyscraper of same height! So much fun! But unfortunately, new skyscrapers have been built recently. Let us describe the problem in one dimensional space

View Solution →

Palindromic Subsets

Consider a lowercase English alphabetic letter character denoted by c. A shift operation on some c turns it into the next letter in the alphabet. For example, and ,shift(a) = b , shift(e) = f, shift(z) = a . Given a zero-indexed string, s, of n lowercase letters, perform q queries on s where each query takes one of the following two forms: 1 i j t: All letters in the inclusive range from i t

View Solution →

Counting On a Tree

Taylor loves trees, and this new challenge has him stumped! Consider a tree, t, consisting of n nodes. Each node is numbered from 1 to n, and each node i has an integer, ci, attached to it. A query on tree t takes the form w x y z. To process a query, you must print the count of ordered pairs of integers ( i , j ) such that the following four conditions are all satisfied: the path from n

View Solution →

Polynomial Division

Consider a sequence, c0, c1, . . . , cn-1 , and a polynomial of degree 1 defined as Q(x ) = a * x + b. You must perform q queries on the sequence, where each query is one of the following two types: 1 i x: Replace ci with x. 2 l r: Consider the polynomial and determine whether is divisible by over the field , where . In other words, check if there exists a polynomial with integer coefficie

View Solution →