# String Equivalence Relations - Amazon Top Interview Questions

### Problem Statement :

You are given three lowercase alphabet strings a, b and target. Strings a and b have the same length and are defined to be equivalent: a[i] = b[i]. For example, if a = "abc" and b = "xyz", then "a" = "x", "b" = "y" and "c" = "z".

Also, we can make the following kinds of inferences for characters:

c = c
a = b implies b = a
a = b and b = c implies a = c

Return the smallest lexicographically equivalent string for target.

Constraints

n ≤ 1,000 where n is the length of a and b
m ≤ 1,000 where m is the length of target

Example 1

Input

a = "axc"
b = "xdz"
target = "ddxz"

Output

"aaac"

Explanation

We know that "a" = "x" and "x" = "d", so "a" = "d". So we can replace the "d"s and "x" with "a"s. Then we can directly replace "z" with "c".

Example 2

Input

a = "abc"
b = "def"

target = "xyz"

Output

"xyz"

Explanation

There's no inferences we can make here.

### Solution :

Solution in C++ :

int findpapa(vector<char> &papa, int c) {
if (papa[c] != c) {
papa[c] = findpapa(papa, papa[c]);
}
return papa[c];
}

string solve(string a, string b, string target) {
vector<char> papa(26);
for (int i = 0; i < 26; i++) {
papa[i] = i;
}
for (int i = 0; i < a.size(); i++) {
// cout<<a[i]-'a'<<" "<<b[i]-'a'<<endl;
int p1 = findpapa(papa, a[i] - 'a');
int p2 = findpapa(papa, b[i] - 'a');
// cout<<p1<<" "<<p2<<endl;
if (p1 < p2) {
papa[p2] = p1;
} else {
papa[p1] = p2;
}
// cout<<"main nhi hagga"<<endl;
}
for (char &c : target) {
int p1 = findpapa(papa, c - 'a');
c = ('a' + p1);
}
return target;
}

Solution in Python :

class Solution:
def solve(self, a, b, target):
parent = {}

def find(x):
if x not in parent:
return x
if parent[x] != x:
parent[x] = find(parent[x])
return parent[x]

def union(x, y):
x0 = parent[x]
y0 = parent[y]
if x0 == y0:
return
if y0 < x0:
x0, y0 = y0, x0
parent[y0] = x0

for c1, c2 in zip(a, b):
if c1 not in parent:
parent[c1] = c1
if c2 not in parent:
parent[c2] = c2
union(c1, c2)

return "".join(find(t) for t in target)

## Equal Stacks

ou have three stacks of cylinders where each cylinder has the same diameter, but they may vary in height. You can change the height of a stack by removing and discarding its topmost cylinder any number of times. Find the maximum possible height of the stacks such that all of the stacks are exactly the same height. This means you must remove zero or more cylinders from the top of zero or more of

## Game of Two Stacks

Alexa has two stacks of non-negative integers, stack A = [a0, a1, . . . , an-1 ] and stack B = [b0, b1, . . . , b m-1] where index 0 denotes the top of the stack. Alexa challenges Nick to play the following game: In each move, Nick can remove one integer from the top of either stack A or stack B. Nick keeps a running sum of the integers he removes from the two stacks. Nick is disqualified f

## Largest Rectangle

Skyline Real Estate Developers is planning to demolish a number of old, unoccupied buildings and construct a shopping mall in their place. Your task is to find the largest solid area in which the mall can be constructed. There are a number of buildings in a certain two-dimensional landscape. Each building has a height, given by . If you join adjacent buildings, they will form a solid rectangle

## Simple Text Editor

In this challenge, you must implement a simple text editor. Initially, your editor contains an empty string, S. You must perform Q operations of the following 4 types: 1. append(W) - Append W string to the end of S. 2 . delete( k ) - Delete the last k characters of S. 3 .print( k ) - Print the kth character of S. 4 . undo( ) - Undo the last (not previously undone) operation of type 1 or 2,

## Poisonous Plants

There are a number of plants in a garden. Each of the plants has been treated with some amount of pesticide. After each day, if any plant has more pesticide than the plant on its left, being weaker than the left one, it dies. You are given the initial values of the pesticide in each of the plants. Determine the number of days after which no plant dies, i.e. the time after which there is no plan

## AND xor OR

Given an array of distinct elements. Let and be the smallest and the next smallest element in the interval where . . where , are the bitwise operators , and respectively. Your task is to find the maximum possible value of . Input Format First line contains integer N. Second line contains N integers, representing elements of the array A[] . Output Format Print the value