CODEFORCES CONTESTS - EPIC Institute of Technology Round August 2024 (Div. 1 + Div. 2) - Removals Game
B. Removals Game
Problem Description
Alice has a permutation a1, a2, ..., an
of [1, 2, ..., n]
, and Bob has another permutation b1, b2, ..., bn
of [1, 2, ..., n]
. They will play a game with these arrays.
In each turn, the following events happen in order:
- Alice chooses either the first or the last element of her array and removes it from the array.
- Bob chooses either the first or the last element of his array and removes it from the array.
The game continues for n-1
turns, after which both arrays will have exactly one remaining element: x
in array a
and y
in array b
.
If x = y
, Bob wins; otherwise, Alice wins. Determine which player will win if both players play optimally.
Input
Each test case consists of multiple cases. The first line contains the number of test cases t
(1 ≤ t ≤ 10^4
). The description of each test case follows:
- The first line of each test case contains an integer
n
(1 ≤ n ≤ 3 × 10^5
). - The next line contains
n
integersa1, a2, ..., an
, which is the permutation for Alice. - The next line contains
n
integersb1, b2, ..., bn
, which is the permutation for Bob.
It is guaranteed that all ai
and bi
are distinct and the sum of all n
does not exceed 3 × 10^5
.
Output
For each test case, print a single line with the name of the winner, assuming both players play optimally. Print “Alice” if Alice wins; otherwise, print “Bob”.
Example
Input
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2
1 2
1 2
3
1 2 3
2 3 1
Output
1
2
Bob
Alice
Note
In the first test case, Bob can win the game by deleting the same element as Alice did.
In the second test case, Alice can delete 3 in the first turn, and then in the second turn, delete the element that is different from the one Bob deleted in the first turn to win the game.
Code
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import java.io.*;
import java.util.*;
public class MinimizeEqualSumSubarrays {
static BufferedReader br;
static StringTokenizer st;
public static void main(String[] args) throws IOException {
// 효율적인 입력을 위해 BufferedReader 사용
// BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
br = new BufferedReader(new InputStreamReader(new FileInputStream("input.txt")));
st = new StringTokenizer(br.readLine());
int tc = Integer.parseInt(st.nextToken());
for (int t = 0; t < tc; t++) {
st = new StringTokenizer(br.readLine());
int n = Integer.parseInt(st.nextToken());
int[] alice = new int[n]; // Alice의 순열을 저장할 배열
int[] bob = new int[n]; // Bob의 순열을 저장할 배열
st = new StringTokenizer(br.readLine());
for (int i = 0; i < n; i++) {
alice[i] = Integer.parseInt(st.nextToken());
}
st = new StringTokenizer(br.readLine());
for (int i = 0; i < n; i++) {
bob[i] = Integer.parseInt(st.nextToken());
}
System.out.println(solve(n, alice, bob));
}
br.close();
}
/**
* 앨리스 배열 양 끝 포인터와 밥 배열 양 끝 포인터 설정
* 앨리스 배열의 양쪽 끝 숫자가 밥 배열 양 끝 숫자와 전부 다르면 앨리스 승리
* 전부 비교할때까지 진행하며 같은것이 계속 있으면 밥 승리
*
* @param n 숫자 개수
* @param alice 앨리스 배열
* @param bob 밥 배열
* @return 승리자
*/
private static String solve(int n, int[] alice, int[] bob) {
int leftA = 0, rightA = n - 1; // Alice 배열의 양 끝 포인터
int leftB = 0, rightB = n - 1; // Bob 배열의 양 끝 포인터
while (leftA <= rightA) {
if (alice[leftA] != bob[leftB] && alice[leftA] != bob[rightB]) {
return "Alice";
}
if (alice[rightA] != bob[leftB] && alice[rightA] != bob[rightB]) {
return "Alice";
}
if (alice[leftA] == bob[leftB]) {
leftA++;
leftB++;
} else if (alice[leftA] == bob[rightB]) {
leftA++;
rightB--;
} else if (alice[rightA] == bob[leftB]) {
rightA--;
leftB++;
} else {
rightA--;
rightB--;
}
}
return "Bob";
}
}