# Alternating Characters

### Problem Statement :

```You are given a string containing characters A and B only. Your task is to change it into a string such that there are no matching adjacent characters. To do this, you are allowed to delete zero or more characters in the string.

Function Description

Complete the alternatingCharacters function in the editor below.

alternatingCharacters has the following parameter(s):

string s: a string

Returns

int: the minimum number of deletions required

Input Format

The first line contains an integer q, the number of queries.
The next q lines each contain a string s to analyze.

Constraints

1  <=   q   <=   10
1  <=  length of s  <=  10^5
Each string s will consist only of characters A and B.

Sample Input

5
AAAA
BBBBB
ABABABAB
BABABA
AAABBB

Sample Output

3
4
0
0
4```

### Solution :

```                            ```Solution in C :

In C++ :

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main() {
int t;
cin>>t;
while(t--)
{
string s;int c=0,a=0;
cin>>s;
for(int i=1;s[i]!='\0';i++)
{
if((s[i]==65 && s[a]==66)||(s[i]==66 &&s[a]==65))
{
a=i;
// cout<<a<<endl;
}
else{
c++;
//cout<<c<<" "<<i<<endl;

}

}
cout<<c<<endl;

}
return 0;
}

In Java :

import java.util.Scanner;
public class Solution {

public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner s = new Scanner(System.in);
int t = s.nextInt();
s.nextLine();
while(t-- > 0)
{
int count = 0;
String str = s.nextLine();
for(int i=1;i<str.length();i++)
{
if(str.charAt(i)==str.charAt(i-1))
{
count++;
}
}
System.out.println(count);
}
}

}

In  C :

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main()
{
int t;
long i=0;
unsigned int count=0;
char * c;
scanf("%d",&t);
c=(char *)malloc(sizeof(char)*(100002));
while(t--)
{
scanf("%s",c);
for(i=0; *(c+i); i++)
{
if(c[i]==c[i+1])
{
count++;
}
}
printf("%u\n",count);
count=0;
}

return 0;
}

In  Python3 :

def f(s):
return sum(1 for c1, c2 in zip(s, s[1:]) if c1 == c2)

t = int(input())
for _ in range(t):
print(f(input()))```
```

## Binary Search Tree : Insertion

You are given a pointer to the root of a binary search tree and values to be inserted into the tree. Insert the values into their appropriate position in the binary search tree and return the root of the updated binary tree. You just have to complete the function. Input Format You are given a function, Node * insert (Node * root ,int data) { } Constraints No. of nodes in the tree <

## Tree: Huffman Decoding

Huffman coding assigns variable length codewords to fixed length input characters based on their frequencies. More frequent characters are assigned shorter codewords and less frequent characters are assigned longer codewords. All edges along the path to a character contain a code digit. If they are on the left side of the tree, they will be a 0 (zero). If on the right, they'll be a 1 (one). Only t

## Binary Search Tree : Lowest Common Ancestor

You are given pointer to the root of the binary search tree and two values v1 and v2. You need to return the lowest common ancestor (LCA) of v1 and v2 in the binary search tree. In the diagram above, the lowest common ancestor of the nodes 4 and 6 is the node 3. Node 3 is the lowest node which has nodes and as descendants. Function Description Complete the function lca in the editor b

## Swap Nodes [Algo]

A binary tree is a tree which is characterized by one of the following properties: It can be empty (null). It contains a root node only. It contains a root node with a left subtree, a right subtree, or both. These subtrees are also binary trees. In-order traversal is performed as Traverse the left subtree. Visit root. Traverse the right subtree. For this in-order traversal, start from

## Kitty's Calculations on a Tree

Kitty has a tree, T , consisting of n nodes where each node is uniquely labeled from 1 to n . Her friend Alex gave her q sets, where each set contains k distinct nodes. Kitty needs to calculate the following expression on each set: where: { u ,v } denotes an unordered pair of nodes belonging to the set. dist(u , v) denotes the number of edges on the unique (shortest) path between nodes a

## Is This a Binary Search Tree?

For the purposes of this challenge, we define a binary tree to be a binary search tree with the following ordering requirements: The data value of every node in a node's left subtree is less than the data value of that node. The data value of every node in a node's right subtree is greater than the data value of that node. Given the root node of a binary tree, can you determine if it's also a