240530 회전 초밥

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer st = new StringTokenizer(br.readLine());
	int n = Integer.parseInt(st.nextToken());
	int d = Integer.parseInt(st.nextToken());
	int k = Integer.parseInt(st.nextToken());
	int c = Integer.parseInt(st.nextToken());

	int[] sushi = new int[n];
	for (int i = 0; i < n; i++) {
		sushi[i] = Integer.parseInt(br.readLine());
	}

	System.out.println(findMaxSushiVariety(sushi, n, d, k, c));
}

private static int findMaxSushiVariety(int[] sushi, int n, int d, int k, int c) {
	int[] count = new int[d + 1];
	int currentVariety = 0;
	int maxVariety = 0;

	for (int i = 0; i < k; i++) {
		if (count[sushi[i]] == 0) {
			currentVariety++;
		}
		count[sushi[i]]++;
	}

	maxVariety = currentVariety;

	for (int i = 0; i < n; i++) {
		if (maxVariety <= currentVariety) {
			if (count[c] == 0) {
				maxVariety = currentVariety + 1;
			} else {
				maxVariety = currentVariety;
			}
		}

		int endIndex = (i + k) % n;
		count[sushi[i]]--;
		if (count[sushi[i]] == 0) {
			currentVariety--;
		}
		if (count[sushi[endIndex]] == 0) {
			currentVariety++;
		}
		count[sushi[endIndex]]++;
	}

	return maxVariety;
}

출처:https://www.acmicpc.net/problem/2531