Cipher Shifer (Codeforces 1840A)
Tags: Implement, strings

There is a string $$$a$$$ (unknown to you), consisting of lowercase Latin letters, encrypted according to the following rule into string $$$s$$$:  after each character of string $$$a$$$, an arbitrary (possibly zero) number of any lowercase Latin letters, different from the character itself, is added;  after each such addition, the character that we supplemented is added. You are given string $$$s$$$, and you need to output the initial string $$$a$$$. In other words, you need to decrypt string $$$s$$$.Note that each string encrypted in this way is decrypted uniquely.

Input: The first line of the input contains a single integer $$$t$$$ ($$$1 \le t \le 1000$$$) — the number of test cases.The descriptions of the test cases follow.The first line of each test case contains a single integer $$$n$$$ ($$$2 \le n \le 100$$$) — the length of the encrypted message.The second line of each test case contains a string $$$s$$$ of length $$$n$$$ — the encrypted message obtained from some string $$$a$$$.

Output: For each test case, output the decrypted message $$$a$$$ on a separate line.

Note: In the first encrypted message, the letter $$$a$$$ is encrypted as $$$aba$$$, and the letter $$$c$$$ is encrypted as $$$cabac$$$.In the second encrypted message, only one letter $$$q$$$ is encrypted as $$$qzxcq$$$.In the third encrypted message, zero characters are added to each letter.

Sample Inputs:
3
8
abacabac
5
qzxcq
20
ccooddeeffoorrcceess

Sample Outputs:
ac
q
codeforces

Solution (Python):
inpt = int(input())
while inpt > 0:
    o = int(input())
    a1 = input()
    k = ''
    i = 0
    while i < o:
        k += a1[i]
        i += a1[i + 1:].index(a1[i]) + 2
    print(k)
    inpt -= 1

Solution (Python):
t = int(input())
for _ in range(t):
    n = int(input())
    s = input()
    ans = 'a'
    while len(s) != 0:
        for i in range(1, n):
            if s[i] == s[0]:
                ans = ans + s[i]
                s = s[i + 1:]
                break
    print(ans[1:])

Solution (Python):
for s in [*open(0)][2::2]:
    r = ''
    p = 0
    for x in s:
        if p == 0:
            p = x
        elif x == p:
            r += p
            p = 0
    print(r)